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
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
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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.
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