Smart viruses that jump species: Covid-19, HIV, Ebola and others…

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By Ricardo Ribas

Image from syaibatulhamdi, pixabay.com
Image from syaibatulhamdi, pixabay.com

Viruses are microscopic agents that infect living organisms and cause diseases. They are considered the most abundant biological entity on the planet, existing for over 1.5 billion years. Viruses have both life and non-life properties. They do not have cells and cannot turn food into energy, but have genetic material (either DNA or RNA). Without a host cell, viruses are inert containers of chemicals so they need to infect cells in order to reproduce, evolve and survive. Hosts can be humans, animals, plants, fungi and bacteria. Some viruses are harmless whilst others cause diseases, some of which leading to the death of the host. To date there are no drugs capable of killing viruses so the host is dependent on its own immune system to fight the infection. Nowadays, there are some antiviral drugs capable of inhibiting them from reproducing and developing, as well as vaccines able to prevent infections and control the spread of the disease.

There are many types of viruses, each one adapted to its own host, but at times, viruses can jump and infect different hosts through a process called “spillover”. This can happen as a result of increased contact between different species or due to mutations that allows the viruses to evolve and gain the capacity to spread more efficiency in order to survive and to become more dangerous. In recent years, we have heard more and more about viral diseases able to jump from animals to humans. Here are some examples:

Influeza: The Flu Viruses

In the last century, there have been many examples of flu-like diseases caused by viruses that jumped from animals to humans. Some are caused by influenza viruses, a family responsible for attacking the respiratory system and causing flu like symptoms in humans.

In 1918, a deadly flu-like pandemic (Spanish Flu) appeared and rapidly spread around the world, infecting 500 million people and killing an estimated of 50 million. There is still some controversy about where the virus was originated from since Europe, America and Asia were affected simultaneously, but recent studies tend to agree that the outbreak may have originated in the North of China, either from pigs or from domestic and wild birds.

But there are other more recent examples of influenza viruses that jump species, such as the ones responsible for the outbreaks of swine-flu and bird-flu.

Although pig’s influenza viruses are rarely transmitted to humans and are hardly spread between people, they were responsible for the worldwide outbreak of swine-flu in 2009-2010. The disease was firstly identified in 2009 when many cases of human respiratory illness were reported in Mexico. We now know that this virus is the result of a merge between genetic material from pigs, birds and human viruses. In animals, the disease is responsible for fever, coughing, nose and eyes discharge, sneezing, breathing difficulties and lack of appetite, however, some animals show no signs of illness. Humans show flu like symptoms and can be infected either by close contact with pigs through farming and fairs or by person-to-person contact during sneezing, coughing and by contaminated surfaces. Fortunately, the 2009 outbreak was not as serious as previously anticipated and only a relatively small number of cases lead to serious illnesses and deaths. Swine flu is now considered a normal type of seasonal flu and is included in the vaccination program.

Bird-flu is another infectious type of influenza that spreads among wild and domestic birds. The most common form of the disease is caused by H5N1, a deadly virus for birds. H5N1 was firstly identified in humans in Hong-Kong in 1997. Human cases of the disease were linked with the handling of faeces, nasal and mouth secretions of infected poultry, particularly in farms and markets. Bird symptoms include: sudden death, lack of coordination, purple discoloration of the wattles, combs and legs, misshapen eggs, diarrhoea, nasal discharge, coughing and sneezing. Humans generally suffer from fever, cough, sore throat, muscle ache but the disease can lead to pneumonia. The disease has high mortality rate and is responsible for causing the death of about 60% of those infected. The good news is that H5N1 only rarely infect humans and is not capable to spread from person to person. In spite of this, it is a fast mutating virus and if it gains the capacity to be transmissible between humans while retaining its capacity to cause severe disease, the consequences can be very serious.

Human Immunodeficiency Virus (HIV): one century with humans

Another example of a virus that crossed species is the one responsible for human immunodeficiency. Once infected, the virus attacks the immune system of the host, opening the door for other opportunistic diseases. This disease was first observed in 1981 in the USA, but scientists believe that humans got infected in the 1920’s in West-Central Africa, possibly in what is now the Democratic Republic of Congo. Scientists believe this happened when hunters consumed meat from non-human primates carrying a virus closely related to the HIV (Simian Immunodeficiency Virus or SIV), a virus that also attacks the immune system of these animals. It is suspected that the infection has reached the Caribbean islands in 1960s, New York City in the 1970’s and San Francisco a decade later, when it was finally discovered.

Ebola, the terrifying virus

The Ebola virus was first discovered in 1976 near the Ebola River in the Democratic Republic of Congo. Since then, the virus has been responsible for occasional outbreaks in human and primates in many African countries. Between 1976 and 2013, the world health organisation reported 24 human outbreaks of the disease with 1.600 deaths in total, but the largest outbreak occurred between 2013 and 2016 and was responsible for over 11.000 deaths. The disease is rare but very severe, often causing fever, sore throat, body aches, vomit, diarrhoea and sometimes bleeding inside and outside the body, with death occurring in 50% of the human infected. Scientist think that the Ebola virus may be carried by bats, because these animals don’t die of the disease. It is believed that humans get infected by contact with the infected animal’s body fluids, either directly from bats or during consumption of nonhuman primates. The virus spreads through human-to-human contact and it is also possible via blood or the body fluids of the infected person.

Coronaviruses repeated stories

Recent history also showed us how coronaviruses can jump from animals to cause a large number of human deaths. Coronaviruses are a large family of viruses known to exist for over 10.000 years. Its name derives from the latin word “corona”, that means crown due to the presence of crown-like spikes in their surface.

Coronaviruses are responsible for respiratory and intestinal diseases in mammals and birds, but the symptoms vary according to the host animal and the type of virus. For instance, in chickens, coronavirus attacks the respiratory and urogenital tracts, whilst in dogs, cats, ferret, rabbits, turkeys, pigs and cows the virus tends to affect the animal’s intestine leading to diarrhoea.

Humans, can only be infected by seven types of coronaviruses. Four of these are very common and responsible for mild respiratory infections with symptoms similar to the ones observed with a cold, but the remaining three viruses can lead to serious and sometimes lethal respiratory infections, such as pneumonia. These include the viruses responsible for the Severe Acute Respiratory Syndrome (SARS), the Middle East Respiratory Syndrome (MERS) and the most recent outbreak in China in 2019-2020 (Covid-19).

SARS was first identified in Southern China during the outbreak of the disease in 2003. Scientists believe that bats are the reservoir of the virus and that the disease was transmitted to humans through consumption of civet cats meat infected by the bats. Once in humans, the disease can spread from person to person. By the end of the outbreak, over 8000 people have been infected and approximately 10% of those died (774 people). Fortunately, no cases of SARS have been reported since 2004.

MERS was reported for the first time in 2012 in Saudi Arabia. It is known that the virus was firstly transmitted to humans by dromedary camels in the earlier 2010s, possibly during consumption of camel meat. This virus has also been found in bats and is believed that it may have infected camels in Africa in the 1990s. Even though the possibility of human to human transmission is very low, the mortality of the disease is quite high standing above 35%. So far, MERS killed 858 out of the 2494 reported cases since it appeared in 2012.

Very recently a new outbreak of coronavirus has emerged in Wuhan, China (Covid-19). Similarly to SARS and MERS, this infection is also responsible for severe acute respiratory infection that can lead to either mild or severe symptoms such as pneumonia, kidney failure and death. Since this is a very recent virus, not much is known about it yet. To date scientists haven’t yet identified which animal the reservoir for the virus is, however, it appears that the contamination to humans may have occurred in a wildlife market, possible during consumption of wild animals. Despite the fact that the rate of transmission between humans is high, the mortality rate seems low. So far, the disease has spread within China and other countries around the world and an international effort is being made to control the spread of the disease.

When human viruses infect animals?

Sometimes viruses can jump the opposite way. There are also examples of human viruses that alter and adapt to infect animals. This is the case of the human respiratory syncytial virus (HRSV) and the human metapneumovirus (HMPV) that have jumped from humans to chimpanzees. It is believed that this has occurred between 1999 and 2006 in West Africa possibly through tourists visiting the area. Whilst these viruses rarely cause severe disease in healthy adult humans, they are responsible for outbreaks of respiratory diseases among African chimpanzees leading to the death of entire populations.

Why are animal-derived outbreaks getting more frequent?

The fast-growing world population and the development of large metropolis are incentives to the expansion of wildlife trade, which favoured diseases to spill over from animals to humans. Additionally, environment and climate changes are shifting animal habitats, altering their life-styles, their geographic locations and their eating habits (who eat whom). Finally, in an era of international travel means that diseases can spread very quickly.

But a question remains. In a world more vulnerable than ever to new animal-borne diseases, what do you think can be done to prevent future outbreaks?

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and researcher in the area of oncology in London

Reference Sources

1.Taubenberger JK & Morens, DM. 1918 Influenza: the Mother of All Pandemics. Emerg Infect Dis. 2006 Jan; 12(1): 15–22. doi: 10.3201/

2.Mena I, Nelson MI, Quezada-Monroy F, et al. Origins of the 2009 H1N1 influenza pandemic in swine in Mexico. Elife. 2016;5:e16777. Published 2016 Jun 28. doi:10.7554/eLife.16777

3. Chan PKS. Outbreak of Avian Influenza A(H5N1) Virus Infection in Hong Kong in 1997. Clinical Infectious Diseases, Vol 34, Suppl. 2, 2002, https://doi.org/10.1086/338820

4. Sharp PM & Hahn BH. Origins of HIV and the AIDS Pandemic. Cold Spring Harb Perspect Med. 2011 Sep; 1(1): a006841. doi: 10.1101/cshperspect.a006841

5. Wertheim JO; Chu, DKW et al. A Case for the Ancient Origin of Coronaviruses. J Virol. 2013 Jun; 87(12): 7039–7045. doi: 10.1128/JVI.03273-12

6. Wang LF & Eaton BT. Bats, Civets and the Emergence of SARS. Curr Top Microbiol Immunol. 2007;315:325-44. doi: 10.1007/978-3-540-70962-6_13.

7. Haagmans, BL; Dhahiry SHSA et al., Middle East respiratory syndrome coronavirus in dromedary camels: an outbreak investigation. Lancet Infect Dis. 2014 Feb; 14(2): 140–145. doi: 10.1016/S1473-3099(13)70690-X

8. Kondgen S; Kuhl H et al., Pandemic Human Viruses Cause Decline of Endangered Great Apes. Current Biology 18, 260–264, 2008 Feb. DOI 10.1016/j.cub.2008.01.012

9. Britt, R. 11 (sometimes) deadly diseases that hopped across species. Live Science. Firstly published 2011, updated by Life Science Staff in 2020. https://www.livescience.com/12951-10-infectious-diseases-ebola-plague-influenza.html. Accessed January 2020

10. Virus. Wikipedia, Wikipedia Foundation. https://en.wikipedia.org/wiki/Virus. Accessed January 2020.

11. Spillover infection. Wikipedia, Wikipedia Foundation. https://en.wikipedia.org/wiki/Spillover_infection#cite_note-2. Accessed January 2020.

12. Spanish flu. Wikipedia, Wikipedia Foundation. https://en.wikipedia.org/wiki/Spanish_flu#Hypotheses_about_the_source. Accessed January 2020.

13. 2009 swine flu pandemic. Wikipedia, Wikipedia Foundation. https://en.wikipedia.org/wiki/2009_swine_flu_pandemic#Signs_and_symptoms. Accessed January 2020

14. Influenza A virus subtype H5N1. Wikipedia, Wikipedia Foundation. https://en.wikipedia.org/wiki/Influenza_A_virus_subtype_H5N1#cite_note-:0-21. Accessed January 2020

15. HIV. Wikipedia, Wikipedia Foundation. https://en.wikipedia.org/wiki/HIV#Origins. Accessed January 2020

16. Coronavirus. Wikipedia, Wikipedia Foundation. https://en.wikipedia.org/wiki/Coronavirus. Accessed January 2020

17. Information on Swine/Variant Influenza. Centers for Disease Control and Prevention. https://www.cdc.gov/flu/swineflu/index.htm. Accessed January 2020

18. CDC – NIOSH Publications and Products – Protecting Poultry Workers from Avian Influenza (Bird Flu) (2008-128)”. http://www.cdc.gov.2008. doi:10.26616/NIOSHPUB2008128. Accessed January 2020.

19. Swine Influenza. World Organisation for animal Health. https://www.oie.int/en/animal-health-in-the-world/animal-diseases/Swine-influenza/. Accessed January 2020

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Disclaimer

The subjects and ideas discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

Holiday Season: what to do with my pets?

With the holiday season approaching, it is time to decide whether to take your pets with you or to leave them at home. Here are some tips to help you make the right decision.

By Ricardo Ribas

Image from   Pexels,  pixabay.com
Image from Pexels, pixabay.com

Taking your pet on holiday can turn out to be a very stressful experience for both your furry friend and your family, so it is essential to start planning it well in advance. Before deciding whether to take your furry friend on a trip, make sure you consult your vet to check their health condition and to advise you what is the best way to proceed. For instance, elderly, pregnant and very young animals as well as the ones with underlying health conditions, may require extra care and may be advised against going on longer trips. Bear in mind that some animals get very stressed whist travelling so it is important to take into account both the distance and the mode of transport before deciding whether to take them. Finally, remember to check the weather conditions at your destination to avoid exposing the animals to very hot temperatures and ensure the access to animal-friendly accommodations, restaurants and other attractions such as beaches, etc.

DECISION TAKEN: THE ANIMAL WILL STAY!!

If you decide against taking your pets on holidays, make sure you plan in advance where to leave them. Like humans, each animal has a different personality and can react differently to the same situation. It is important to remember that a separation of the animal from its owner usually causes some degree of anxiety. Some animals respond well to separation, particularly if they stay with acquaintances and in familiar surroundings, whilst others may exhibit behavioural changes such as stopping eating, lethargy, sadness or even aggression. In order to minimize their anxiety, it is important that the you start adapting the animal to the place and the person who will be taking care of them during your absence. Ideally, leave your pet at your home and invite a friend or a family member to stay at your house, but if this is difficult, there are several kennels, hotels or animal sitters that are happy to take care of your pet during your absence. It is important to visit the facility well in advance to examine if it is good enough for your animal. Be aware of the hygiene, size, light, exercise area, food, veterinary assistance, employees, as well as the risk of your animal being infected by any potential diseases. Also remember that many places require an advanced reservation so plan well in advance. If you leave the animal at one of these places, it is a recommended that you bring some of the animal’s toys, as well as their bed or basket and a piece of the owner’s clothing with their scent so that the animal feels more comfortable. Make sure you instruct the carer about the animal’s habits as well as their food requirements. Finally, leave your contact details as well as your vet’s for any eventualities and ask for regular updates whilst you are away.

Never in any circumstances abandon your pet. An animal left without any human protection will feel lonely which can lead to extreme anxiety and psychological disturbances.

THE ANIMAL TRAVELS WITH YOU…

If you decide to take your animal on holidays, it is important to plan the trip well in advance and to choose the safest and most comfortable way of transportation, making the animal’s experience as comfortable as possible.

Travelling by car is usually the best option, but some precautions should be taken. Other easy options include train or boats/ferry where owners are usually allowed to take their pets with them, often with a charge attached to it. It is important to make sure owners prepare their animals for the long trip ahead by taking them for short test drives. During the trip, always carry cold water for the animal and never leave your animal inside the car, on its own, specially in hot weather. Make sure you stop regularly to allow for short exercises and keep in mind that some animals get very stressed on a trip, so avoid feeding them too much beforehand to prevent them from vomiting or having diarrhoea.

Travelling by air requires a lot of planning and should only be considered if there are no other alternatives. If travelling abroad, remember that each country has its own legislation regarding animal arrivals so check in advance with your airline, your vet and the country destination for the specific requirements and regulations. Animals often require to be microchipped and to show their documents confirming they are fit and healthy to travel and to enter the country. Some countries also required a pet-passport and a proof of vaccinations and in some instances quarantine measures may apply. It is also highly recommended to have a pet insurance covering trips abroad in case the animal gets sick whilst in a different country.

Always contact your airline well in advance, making sure you reserve a place for your pet and that you understand the animal transportation conditions. Each airline has its own policies and some flights may not be licensed to carry animals, whilst others may only accept a certain number of animals per flight. In some instances airlines may allow you to take small pets with you inside the plane under the seat, but often animals are required to go in the hold under the plane, generally in pressurised conditions similar to the ones in the cabin. If in the hold, the animal will need to be carried inside a special container or box with an adequate size to allow the animal to sit, stand and rotate inside. Assistance and guide dogs are usually allowed in the cabin and can travel for free, but make sure you inform and confirm this with your airline.

Ahead of your flight, make sure you prepare everything for the animal’s comfort and safety, such as:

• Place an identification tag in the animal collar as well as in the container displaying your name, address at destination and your phone number.

• If the animal is travelling in the hold, make sure the details on their tickets are the same as the ones on your ticket and that the tag attached to the container is correct.

• Feed the animal earlier in the day and make sure they are relieved before putting them in the container. For animals that get very stressed during the trip and often vomit, consider withholding food for a minimum of 2-4 hours before the flight. Ask the vet for some medication to prevent it from happening.

• Make sure you include food and water packs within the container particularly for long flights

• Exercise the animals before the trip to tire them. The use of tranquilizers should be avoided because they affect the way dogs and cats control their body temperature.

• Place their blankets and toys inside the transport container.

• Make sure a container has a secure closure, but that allows for opening in an emergency.

Independent of the way you travel with your pet, always remember to take with you:

• Animal documentation such as the health documents and the vaccination certificates.

• The pet passport if you are travelling abroad

• A lead as well as a collar containing the complete identification.

• The animal’s bed or basket

• Bottle of cold water for the trip

• The animal’s toys, food, plates, poo bags and muzzle (if necessary).

Extra care in the summer:

• Like us, animals can suffer sunstroke, dehydration and sunburn – often on their pads – so walking in the street during peak hours should be avoided.

• Parasites such as fleas and ticks are more common in hot months, so make sure you deworm your animal to avoid discomfort and the possibility of catching infections.

• The beach must also be avoided if possible. Dogs can be vehicles of a worm called Ancylostoma caninum, which spreads through their faeces and can penetrate human skin, causing itching. If you take your dog to the beach, don’t forget to deworm him/her beforehand. Also be careful when taking your dog to the sea as water often penetrates the animal’s ears and can lead to infections, particularly in those animals with droopy ears. Cotton can be used to avoid water from entering. If you decide to take your dog to the beach, protect him/her from the sun to avoid sunburn and always carry a bottle of fresh water. Finally, remember to keep your pet on a lead to prevent them from escaping, becoming lost or bothering others.

Enjoy your holidays and love your pet in all seasons!!!

Ricardo Ribas

Veterinary doctor, doctorate in veterinary sciences and researcher in the area of oncology in London

Reference Sources

1. Bring your pet to the UK: step by step. Gov.uk. https://www.gov.uk/bring-your-pet-to-uk. Accessed June 2020

2. Travelling abroad with dogs. Blue Cross for Pets. https://www.bluecross.org.uk/pet-advice/travelling-abroad-dogs. Accessed June 2020

3. Delaney Ross. How to fly with a pet on a plane. National Geographic. https://www.nationalgeographic.com/travel/features/how-to-fly-with-pet-on-airplane/. Accessed July 2020.

4. Travelling with Your Dog on a Plane. Purina. https://www.purina.co.uk/dogs/behaviour-and-training/travelling-with-your-dog/taking-your-dog-on-the-plane. Accessed July 2020.

Disclaimer

The material, ideas and recommendations discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

Animals and the Covid-19 Pandemic

A virus pandemic has struck the world in 2020. Coronavirus disease 2019, or Covid-19, is an infectious respiratory disease firstly identified in Wuhan, China in December 2019 and has since spread to every corner of the world, killing many hundreds of thousands of people. A lot of research is still necessary to understand the disease and the virus that causes it, yet scientists believe it was originated in animals. But what do we know so far about the role of animals in the emergence of this disease and which animal is the most likely to have transmitted the virus to humans? Can animals also be affected by Covid-19 and how can they help us in fighting the disease? Discover some answers for these and other questions in the following article…

By Ricardo Ribas

Image from Fernandozhiminaicela, pixabay.com
Image from Fernandozhiminaicela, pixabay.com

Understanding Coronaviruses…

Coronaviruses are a large family of viruses that have existed for over 10,000 years. The name derives from the latin word “corona” that means crown due to the presence of crown-like spikes in the virus surface. Coronaviruses are often responsible for respiratory and intestinal diseases in mammals and birds but symptoms can vary according to the host as well as with the type of virus involved. For instance, in chickens, coronaviruses tend to attack predominantly the respiratory and urogenital tracts, whilst in dogs, cats, ferrets, rabbits, turkeys, pigs and cows it affects predominantly the intestines and digestive systems leading to diarrhoea.

Humans can also be infected by coronaviruses. So far there are seven types of coronaviruses known to infect humans, four of which are responsible for mild respiratory infections and three that lead to serious and sometimes lethal respiratory infections, such as pneumonia. These include the Severe Acute Respiratory Syndrome (SARS), a disease initially discovered in China in 2003; the Middle East Respiratory Syndrome (MERS), first found in Saudi Arabia in 2012; and the most recent outbreak that started in China in 2019-2020 (Covid-19), all of which believed to have been transmitted from animals to humans.

All the three coronaviruses responsible for serious infections (SARS, MERS and Covid-19) appear to be originated in bats, that is believed to be the natural reservoir. Bats are often reservoir organisms due to their tolerant immune systems, what allows the viruses to live and reproduce in their bodies without causing any disease. But to be able to reach and infect humans, these viruses generally need an intermediate host animal. In the case of SARS, it is believed that the disease has jumped to humans through the consumption of civet cats previously infected by bats, whilst in the MERS, it is though that the transmission has occurred through dromedary camel’s meat. Scientists are still trying to understand the intermediary specie for the Covid-19 virus but it appears to have happened in a wildlife market probably during consumption of animal products. To try to identify the intermediate animal, researchers have compared the genomic sequence of the human coronavirus responsible for Covid-19 and other coronaviruses that infect several animals and they have discovered large similarities with the virus that infect pangolins, indicating that this is the most likely intermediate host.

But, can animals also get sick from Covid-19?

A lot of research is still necessary to better understand this virus, but the good news is that it looks like animals are not playing a significant role in the spread of the human disease and the risks of animals spreading Covid-19 to humans is low. To date, only a few but very exceptional cases have been reported of humans contaminating animals and one case in which animals have transmitted the virus back to humans. The Netherlands government reported in April 2020 that several minks suffering from respiratory symptoms tested positive for Covid-19 in four different farms possibly infected by humans. More recently, it was announced that two farm workers have now been infected from one of those animals, in what appears to be the first European case of transmission from animals to human. Similarly, several tigers and lions in the New York Zoo also tested positive for the disease after showing symptoms of a cough and loss of appetite. Scientists believe these animals may have been infected by a member of staff carrying the virus, however investigations are still ongoing. Similarly, there have been a small number of cases of confirmed Covid-19 reported in dogs and cats suffering from diarrhoea, vomiting and shortness of breath after being in close contact with people infected by the virus.

Several studies are underway in laboratories to understand which species can or cannot be infected by the disease. Preliminary data in a small number of animals have shown that cats, ferrets and hamsters can be easily infected by the virus and transmit it to other animals of the same species, but that dogs appear to be less sensitive to infection, whilst pigs, chickens and ducks failed to become infected.

As we learn more about this disease and the way it can affect animals, governments around the world are recommending to treat pets in the same way as we would treat other members of our household, to wash the hands frequently before and after handling animals and their food, and to contact the vet if have any questions.

How can animals help scientists fighting and understanding the disease?

Many efforts are ongoing to develop new methods of diagnosis and to discover new treatments and vaccines. To achieve that, scientists are taking advantage of animals to help them answer some of these questions.

It is already known that some dogs can efficiently detect the odour of many human diseases such as cancer, Parkinson’s diseases, diabetes and malaria. Scientists in the UK (at the London School of Hygiene and Tropical Medicine and Durham University) and around the world are now trying to find out if trained sniffer dogs can also be able to reliably detect Covid-19 infections in people even before symptoms appear. So far, preliminary studies seem promising and if successful, this could unleash a new non-invasive tool and a potent early warning measure to detect coronavirus and to help control the spread of the disease.

Some other studies and trials are underway to learn if llamas can help protect humans against this virus. Humans produce antibodies, proteins that recognise the virus and attach to their surface to help in destroying it, but scientists have found that camels, llamas and alpacas produce a small version of these antibodies, called nanobodies. Due of their smaller size, nanobodies are more stable and capable of attaching and sneak into certain pockets of the virus surface, that otherwise human antibodies would struggle. Studies in Belgium have previously shown that nanobodies derived from llamas are efficient in fighting SARS and MERS and scientists are now working towards clinical trials to understand if this is also possible against Covid-19.

Apart from dogs and llamas, scientists also take advantage of other species to help study the disease and to develop vaccines and new treatments. Mice are often used to test the safety of vaccines and therapies before testing in humans. Due to its close proximity with humans, non-human primates such as monkeys are used to help understand how the virus work inside the body, as well as to test the safety and the efficacy of new treatments or if people can be repeatedly infected by the virus. Finally, researchers are taking advantage of other species, such as ferrets, hamsters and cats, because they are good models of the disease or because they can be easily genetically modified to become susceptible to Covid-19 infection.

But, why are animal-derived diseases getting more frequent nowadays?

In the last century, we have witnessed a rapid emergence of new infectious diseases transmitted from animals to humans (zoonosis), such as Ebola, HIV, Swine-Flu, Bird-Flu and several coronavirus infections like SARS, MERS and now Covid-19. But why are these outbreaks becoming more frequent? The fast-growing world population and the development of large metropolis are pushing animals away from their natural habitat, allowing humans to intermingle with wildlife and encouraging the trade of isolated groups of animals often carrying microorganisms to which humans have never been in contact with. Additionally, environmental and climatic changes are causing alterations in temperature and rainfalls therefore shifting animal habitats and ecosystems, altering life-styles, geographic locations and eating habits (who eat whom). The increasing consumption of animal meat is another important factor contributing to the rise of zoonosis as a result of the increased consumption of wild animals, the intensification of greenhouse gas emissions and the deforestation of massive areas for farming and the animal food industry. Finally, and to worsen the situation, the escalation of international travel further contributes to the rapid spread of these diseases.

History has repeated itself and humans are once again suffering the consequences of altering Earth’s habitats and environments. Hopefully lessons will be learned from this pandemic, helping reshape human’s future decisions.

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and researcher in the area of oncology in London

References

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11. Bronx Zoo Tigers and Lions recovering from Covid-19, WCS news Release, 21 April 2020, https://newsroom.wcs.org/News-Releases/articleType/ArticleView/articleId/14084/Update-Bronx-Zoo-Tigers-and-Lions-Recovering-from-COVID-19.aspx

12. Toby Sterling, Mink infected two humans with coronavirus: Dutch gov’t, world news, 25 May 2020, https://www.google.co.uk/amp/s/uk.mobile.reuters.com/article/amp/idUKKBN2311QA

13. COVID-19 / SARS-CoV-2, AnimalResearch.info, 2020. http://www.animalresearch.info/en/medical-advances/diseases-research/sars-cov-2/, Last edited: 30 April 2020, Accessed June 2020

Disclaimer

The material and ideas discussed in this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

Ticks: the vampire of the parasites

Spring has sprung and unlocked the tick’s season. Learn more about this blood eater parasite and which diseases it can bring to you, your family and animals.

By Ricardo Ribas

Image from 272447, pixabay.com
Image from 272447, pixabay.com

UNDERSTANDING THE TICKS?

Ticks are small external parasites that together with the spiders, mites, harvestmen and scorpions form the group of the arachnids. Arachnids are a type of invertebrated animals with their bodies divided into two main compartments: the cephalothorax, corresponding to the front part of the body (containing the head and thorax) and the abdomen. Adults ticks are usually 3-5mm long, ovoid or pear-shaped with eight legs that often become engorged as they feed on blood. Blood is essential for the ticks life-cycle and survival, hence their dependence on vertebrate animals, such as mammals, birds, reptiles, amphibians, as well as humans. But, as blood-eaters, ticks can cause considerable harm to their host either directly or indirectly by transmitting infectious agents. There are more than 800 species of ticks worldwide subdivided into two major groups, according to the presence or absence of a dorsal hard shield: the Ixodidae or hard ticks and the Argasidae also called soft ticks. Hard ticks are the most abundant in nature, accounting for more than 650 of the known species, whilst the soft ticks account for about 155 species. Fossil records suggest that ticks are very old parasites, having been around for over 90 million years.

WHERE DO THE TICKS LIVE?

Ticks are widely distributed around the world, but prefer humid and warm conditions. Spring is their favourite season coinciding with the time when people and animals spend longer periods outside. To help them locate blood, ticks possess senses that attract them to the host smells and body temperatures. Additionally, they often position themselves strategically, such as in tall grasses, which provides them in an ideal spot to crawl and ride into passing hosts. Once attached to the host, ticks can appear anywhere in the body but they often opt for warm and moist areas, such as the armpits, groin and scalp in humans and the head, ears, anus and between the digits in animals.

MORE ABOUT THEIR LIFE CYCLE…

Ticks life-cycle is divided into four main stages: eggs, larva, nymph and adult. Both males and females attack together, but it is easy to distinguish because the females tend to increase their volume, as they feed in blood. Each adult female can produce between 2,000 and 20,000 eggs at one time, often laying them in areas of moist vegetation, where they have higher chances of meeting the hosts. Depending on the species, ticks may require one, two or three hosts.

HOW HARMFUL ARE THEY?

Ticks can seriously harm and even kill their hosts, raising concerns for public health. As blood-eaters, they are often responsible for anaemias, skin inflammations and allergies, conditions particularly serious in livestock and accountable for serious repercussions in the wool and animal-source food industries. Some types of ticks can also produce neurotoxins that can cause paralysis or even lead to death of their host. Luckily, toxicity can be reversed by removing the tick. However this should be done carefully to avoid leaving traces of the tick’s mouth in the host’s skin.

Recent studies have also shown that some ticks are responsible for a type of food allergy to red meat, called Alpha-gal syndrome. When feeding on animal’s blood, particularly cattle and sheep, ticks ingest a sugar molecule called alpha-gal. This sugar is stored in the tick’s saliva and subsequently injected in the human’s bloodstream as they feed. In some people, this triggers a strong immune response that culminates with the development of allergies after consumption of red meat often accompanied by hives, itchy skin, swelling of the lips, tongue, throat and face, abdominal pain, diarrhoea and vomiting, wheezing and shortness of breath. Interestingly, alpha-gal syndrome sufferers do not require to become fully vegetarians, as fish and poultry meat consumption does not trigger the reaction. Unlike most food allergies, alpha-gal allergy can disappear over time.

However, ticks are also be involved in the transmission of infection diseases caused by bacteria, viruses and parasites. Tick-Borne Relapsing Fever and Lyme diseases are examples of bacterial infections transmitted by ticks. Tick-Borne Relapsing Fever is predominantly found in North America, Africa, Asia, Middle East and Spain causing fever and flu-like symptoms in humans, dogs, horses, cattle, deer, mice, chipmunks and racoons. Lyme disease is present mainly in North America and Euroasia. The majority of the animals infected by this disease rarely show symptoms, but dogs often develop fever, lameness and joint pain (arthritis), that in rare cases can develop to heart and kidneys complications and death. Human experience flu-like symptoms accompanied by a red bump in site of the bite that can spread into a larger circular red rash. In some cases, the disease can progress and spread to other organs causing joint pain as well as heart and brain complications. Antibiotics are effective, particularly if administered in the earlier stages.

Other examples of bacterial infections carried by ticks are Ehrlichiosis, Anaplasmosis and Rocky Mountain Spotted Fever, all caused by a Rickettsial-like bacteria, an obligate intracellular microorganism transmitted by arthropods. Ehrlichiosis and Anaplasmosis are globally distributed and responsible for attacking and destroying the host’s white and red blood cells, respectively. Rocky Mountain Spotted Fever is mainly present in the USA and once inside the host it attacks the blood vessel cells. All conditions affect humans and dogs causing fever, flu-like symptoms, diarrhoea, weight loss, anaemia and bleeding disorders such as presence of blood in the urine as well as the presence of erythema and small red rashes in the skin and the conjunctiva caused by broken blood vessels. Antibiotics are efficient, but if delayed, can lead to brain damage, respiratory failure and, in the case of the Rocky Mountain Spotted Fever, to hearing complications and the loss of parts of the limbs. All conditions could lead to death if not treated.

Finally, Tularemia or Rabbit fever is another example of a rare and highly contagious bacterial disease, particularly found in North America and Euroasia and characterised by the appearance of skin ulcers in humans, dogs, cats, rabbits and rodents. Antibiotics are efficient to prevent complications and death.

Nevertheless, ticks are not only vectors of bacteria. They can also transmit parasites such as the case of the Babesia, a single cell organism belonging to the group of protozoa. Babesiosis or Cattle Tick-Fever is a global distributed disease, affecting both humans as well as wild and domestic animals. Once inside the host, the protozoa attack and destroys the red blood cells and leading to flu-like symptoms, dark-colour urine and jaundice, a yellowing of the skin and mucous membranes due to a bile disorder. In severe cases, the parasite can travel to other parts of the body such as the kidneys, lungs and brain and cause incoordination and potential death. Despite the fact that a wide range of animals can be affected, babesiosis is particularly concerning in cattle and buffalo due to the economic impact imposed in cattle industry. Unfortunately, the disease appears also to blame for many wild life causalities over the years, such as the outbreak in Tanzania in early 2000s that killed many rhinos, lions, buffalos, wildebeest and zebras. Fortunately, antibiotics, quinine and vaccination are effective to treat and prevent the disease.

Finally, ticks can also transmit viruses such as the ones responsible for the Powassan disease in North America and the Tick-borne encephalitis in Euroasia, both affecting the brain and causing a variety of neurological symptoms in humans including mental confusion, loss of memory, seizures, difficulties in speech and lack of coordination. Tick-borne encephalitis can also affects carnivores, ruminants, horses, birds and rodents. Other examples of viral diseases include Colorado Tick Fever in the western parts of North America and the Crimean-Congo Haemorrhagic Fever, a disease endemic in Africa, Middle East and Asia. Whilst often asymptomatic in animals, CCHF can cause serious problems in humans leading to bleeding of the skin and mucosa and responsible for death in 40% of the cases, constituting a public health threat. Unfortunately, antibiotics are not efficient in the treatment of these virus diseases, so prevention is the preferable strategy.

PREVENTION: TOP PRIORITY

The best way to avoid and control tick’s infestations is to implement prevention measures. Here are some tips:

• Use insect repellents both in humans and animals. A wide variety of sprays, powders, topical products, shampoos and collars for animals are available in the market.

• Try to cover up with clothes when going to grassy and bushy areas

• Whenever find a tick, remove it with gloves or tweezers by grasping it near the mouth to avoid leaving traces of the tick’s mouth on the host’s skin. After removal, burn the tick, disinfect the area and wash your hands in soap and water.

• If notice ticks in your garden, apply mite sprays.

• Inspect frequently for the presence of ticks on yourself, children and on the animals, especially in areas where ticks regularly appear.

• Vaccinate humans and animals against some of the tick-borne diseases, such as Lyme disease and babesiosis, which have an efficiency of 70 to 100 percent.

• People affected by alpha-gal syndrome should refrain from eating red meat.

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and researcher in the area of oncology in London

Reference Sources

1. Simon LV, West B, McKinney WP. Tick Paralysis. [Updated 2020 Apr 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan. 2020 Apr 28. PMID: 29262244

2 Mabelane T, Ogunbanjo GA. Ingestion of mammalian meat and alpha-gal allergy: Clinical relevance in primary care. Afr J Prm Health Care Fam Med. 2019;11(1), a1901. https://doi.org/10.4102/phcfm.v11i1.1901

3. Elelu, N. Tick-borne Relapsing Fever as a Potential Veterinary Medical Problem. Vet Med Sci. 2018 Nov;4(4):271-279. doi: 10.1002/vms3.108.

4. Chomel, B. Lyme Disease. Rev Sci Tech 2015 Aug;34(2):569-76.doi: 10.20506/rst.34.2.2380.

5. Ismail, N; Bloch, KC; McBride, JW. Human Ehrlichiosis and Anaplasmosis. Clin Lab Med. 2010 Mar;30(1):261-92. doi: 10.1016/j.cll.2009.10.004.

6. Nijhof, AM; Penzhorn, BL et al. Babesia bicornis sp. nov. and Theileria bicornis sp. nov.: Tick-Borne Parasites Associated with Mortality in the Black Rhinoceros (Diceros bicornis). J Clin Microbiol. 2003 May; 41(5): 2249–2254. doi: 10.1128/JCM.41.5.2249-2254.2003

7. Shi, J; Hu, Z et al. Tick-Borne Viruses. Virol Sin 2018 Feb;33(1):21-43. doi: 10.1007/s12250-018-0019-0.

8. Tick, Wikipedia, Wikipedia Foundation, Last update: 30 April 2020. https://en.m.wikipedia.org/wiki/Tick, Accessed May 2020

9. Tick-borne disease, Wikipedia, Wikipedia Foundation, Last update: 25 April 2020. https://en.m.wikipedia.org/wiki/Tick-borne_disease. Accessed May 2020

10. Tularemia. Wikipedia, Wikipedia Foundation, https://en.m.wikipedia.org/wiki/Tularemia. Accessed May 2020

11. Ticks, Centers for disease Control and Prevention, last reviewed 28 May 2020, https://www.cdc.gov/ticks/index.html, Accessed May 2020

12. Carter, PD & Rolls, P. Babesiosis. MSD Manual, Veterinary Manual. Last update: Feb 2015. https://www.msdvetmanual.com/circulatory-system/blood-parasites/babesiosis. Accessed: May 2020

Disclaimer

The material, ideas and prevention measures discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.

Insects that transmit deadly parasite…

Leishmaniasis is an infectious disease endemic in nearly 100 countries around East Africa, the Americas, Southeast Asia and the Mediterranean. It belongs to the list of neglected tropical diseases together with rabies and dengue, despite the fact that the World Health Organization estimates that over 1 million humans are infected each year, making it one of the most dangerous and deadly tropical parasitic diseases, after malaria. The agent is a single-cell parasite named Leishmania and is spread via the bite of infected female sandflies.

Learn more about one of the oldest and more mysterious diseases of mankind, responsible for thousands of deaths around the world yearly.

By Ricardo Ribas

Image from  272447, pixabay.com
Image from 272447, pixabay.com

Leishmaniasis is an endemic disease that affect humans and animals in tropical and subtropical regions around the world, particularly in countries affected by malnutrition, poor housing conditions and a lack of financial resources. Not every human infected develops symptoms, but children, the elderly and people with a weakened immune system, are the more vulnerable groups.

WHO IS THE AGENT?

Leishmaniasis is caused by a microscopic single-cell parasite named Leishmania and is spread by the bite of infected female sandflies. There are over 90 species of sandflies around the world known to transmit the disease to animals and humans. Adult sandflies are small measuring around 3mm, yellow, with black eyes and hairy all over their body, wings and legs.

In nature, Leishmania can be found in two different forms according to the stage of their life-cycle and the host they infect. The promastigote form corresponds to the phase of the cycle when the parasite is living inside the sandfly, whilst the amastigote form is present in the vertebrate (humans or animals). In order to complete the life cycle, the leishmania needs to pass through both hosts, hence the transmission between vertebrates is only possible via the sandfly’s bite.

HOW IS IT TRANSMITTED?

Leishmaniasis is transmitted to humans and animals through a bite of an infected female sandfly while feeding on blood required for their eggs production. After biting the animal, the sandfly ingests the infected blood containing the amastigote parasites allowing them to lodge in their intestine, multiply and convert into the promastigote form. When the sandfly bites the animal or the human again, it deposits the parasite back into their blood. The parasites penetrate the vertebrate’s defence cells, multiply and are transported to the various parts of the body causing damage to the different organs. Fortunately, not all individuals get sick and hosts with a good immune system are able to destroy the parasite and prevent damage.

Transmission is more likely to occur in the warmer months when there are an increased number of sandflies, and usually during dusk and dawn, when the insects are most likely to be looking for food. Once infected, it may take months or even years for the host to develop symptoms.

HOW DOES IT AFFECT ANIMALS?

Over 70 species of animals can be natural reservoir for the Leishmania parasites. These include cats, goats, wolfs, rabbits, rodents and even birds, but dogs seem to be the main reservoir of the disease. Leishmaniasis can affect any breed of dog, yet middle-aged German Shepherds, Boxers and Dobermanns are more susceptible. Males and females are equally affected, but the disease is rare in animals with less than six months. The disease is slow and progressive, and can lead to a wide variety of symptoms such as: painless skin lesions and hair loss in the biting site; fever; lack of appetite; weight loss; diarrhoea and vomiting; swelling of the lymph nodes; conjunctivitis and blindness due to the presence of the parasite in the eyes; lameness and joint inflammation; enlargement of spleen and liver as well as serious kidney problems that can lead to the animal’s death. Cats can also develop the disease and suffer from symptoms similar to the dogs. Due to the presence of nonspecific symptoms, diagnosis can be challenging, often requiring specific blood tests. At times animals may show no symptoms, making it important to perform periodic screening tests particularly to animals inhabiting endemic regions.

AND HOW DOES IT MANIFESTS IN HUMANS?

Humans are generally more resistant to leishmaniasis infection than dogs, however immunocompromised individuals, as well as children and elderly people tend to be more susceptible. Direct transmission between animals and humans is not possible unless via the insect vector.

Humans can be affected with three forms of the disease:

1) Cutaneous is the most common form of the disease, characterised by the presence of skin lesions in the insect biting site, as well as the presence of painless ulcers leaving life-long scars and serious disability;

2) Visceral or Kala-azar is the most serious form of the disease affecting internal organs. If left untreated, it can be fatal in over 95% of the cases. Symptoms are similar to the ones observed in animals, including fever, weight loss, anaemia and enlargement of the spleen and liver. Most cases occur in Brazil, East Africa and in India.

3) Mucocutaneous: is a form of the disease that affects predominantly the mucous membranes and skin of the nose, mouth and throat. More than 90% of the cases occur in South America (Bolivia, Brazil, Peru) and Ethiopia.

WHAT ARE THE RISK FACTORS FOR THE DISEASE?

Many factors affect the likelihood of contracting the disease. Poverty particularly in developing countries, where people live in overcrowded and under bad sanitary conditions, as well as certain human behaviours such as sleeping outside, increases the risk of contracting the disease, creating more opportunities for the insects to breed, to find resting sites and to have more access to human or animal blood. Malnutrition is also a very important risk factor since it compromises the host’s immune system and its capacity to fight the parasite.

Environmental, climate and urbanisational changes are also vital. For instance, human expansion into forested areas and subsequent deforestation affects insect’s numbers, distribution and survival, creating ideal opportunities for the spread of the disease outside the endemic regions.

Treatment of leishmaniasis is possible but involves long duration therapies generally administered into the vein. Its success is also dependent on multiple factors, such as the form of the disease, the type of leishmania as well as the capacity of the host’s immune system to get rid of the parasite. Is important to remember that if left untreated, leishmaniasis can kill.

HOW CAN WE CONTROL AND PREVENT THE DISEASE?

Although several laboratories are trying to develop vaccines against the disease, these are still not effective and the reason why preventive measures are crucial. Here is some advice:

1. Early identification of the disease in humans and animals is crucial to prevent its spread and allow proper and quick treatments.

2. In endemic regions, avoid leaving pets outside the house, particularly at dawn and dusk, since insects are more likely to be looking for food.

3. Use repellents and insecticides in humans in animals and in the environment to keep kennels and homes free from insects. The use of mosquito nets is equally effective, particularly in endemic areas.

4. Perform periodic screening tests on animals inhabiting endemic regions.

6. Educate the community about the disease, prevention measures and encourage behavioural changes.

It is crucial to increase the focus on this neglected disease by helping implement control and prevention measures as well as promoting research to discover new treatments to avoid many thousands of deaths each year.

By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and researcher in the area of oncology in London

References sources

1. Sumter, J & Gull, K. Shape, Form, Function and Leishmania Pathogenicity: From Textbook Descriptions to Biological Understanding. [published correction appears in Open Biol. 2018 Aug;8(8):]. Open Biol. 2017;7(9):170165. doi:10.1098/rsob.170165

2. Ribeiro, RR; Michalick, MSM et al. Canine Leishmaniasis: An Overview of the Current Status and Strategies for Control. Biomed Res Int. 2018. doi:10.1155/2018/3296893

3. Leishmaniasis. World Health Organisation. 2 March 2020. https://www.who.int/news-room/fact-sheets/detail/leishmaniasis & https://www.who.int/leishmaniasis/disease/en/. Accessed April 2020

4. WHO Report on Global Surveillance of Epidemic-prone Infectious Diseases – Leishmaniasis. World Health Organisation. https://www.who.int/csr/resources/publications/CSR_ISR_2000_1leish/en/. Accessed April 2020

5. Parasites- Leishmaniasis. Centre for Disease Control and Prevention. Last updated February 2020. https://www.cdc.gov/parasites/leishmaniasis/index.html. Accessed April 2020

6. Leishmaniasis. Wikipedia, Wikipedia Foundation. https://en.m.wikipedia.org/wiki/Leishmania. Accessed April 2020

7. Leishmaniasis in other animals. Stop leishmania.org. http://www.stopleishmania.org/leishmaniosis-animals.php. Accessed April 2020

Disclaimer

The material, ideas as well as control and prevention measures discussed on this article are for informational purposes only. For more information consult a vet or a professional in the area. Whilst every effort is made to make sure the article is accurate at the time of publication, I take no liability for any new developments on the subject as well as any errors or omissions.