WHEN ANIMALS GET DEMENTIA…

Image from waldryano, pixabay.com

The nervous system is the part of the body responsible for the coordination of the actions and behaviours. It does this by using a complex network of nerves and cells responsible to transmit messages between the brain, the spinal cord and the other parts of the body. The cells responsible for this function are called neurons and have properties that allow them to transmit very rapid and precise signals to the other cells in the body.

 

Nervous systems are present in most multicellular animals, with the exception of the sponges and very small “bloblike” organisms. Nonetheless, it varies a lot in complexity between the animals. Just like humans, animals are born with a fixed number of neurons. One characteristic of the neurons is their inability to divide or multiply, resulting in progressive loss as the animal gets old. This is usually the result of natural ageing processes, but in some cases, neurons can be destroyed at a faster rate than normal resulting in neurodegenerative diseases. These are debilitating and incurable pathologies characterized by a progressive and irreversible destruction of the neurons.

With the exception of the elephant, humans have the largest number of neurons in their body (approximately 100 billion), followed by gorillas (33 billion) and chimpanzees (22 billion). Cats and dogs have approximately 800 and 160 million neurons, respectively. 

 

Recently, the incidence of neurodegenerative diseases has been rising both in humans as well as in domestic animals. This is mainly the result of the new scientific advances in medicine and subsequent increase in life expectancy. But not all neurodegenerative diseases occur in the elderly. Some are hereditary and can affect predominantly young animals and children.

At present, there is no cure for these diseases and the only therapies available are designed to delay cell death and slow down disease progression. Consequently, early detection of the symptoms is of paramount importance to prevent disease progression. Nonetheless, the diagnosis becomes more difficult in animals, given that the symptoms are less obvious than in humans.

 

Many neurodegenerative diseases are very similar between humans and animals. For instance, dogs and cats can often suffer from a type of dementia equivalent to the Alzheimer’s disease in humans called “cognitive dysfunction syndrome”. Just like in humans, this pathology tends to affect predominantly elderly animals and is a result of the accumulation of a toxic protein (beta-amyloid) in the brain. With the time, this neurotoxin form deposits that will cause changes in the brain and slowdown the mental function, resulting in alterations in behaviour and in the daily routines. The animals often lose memory and experience walking problems, incontinence, anxiety, aggressiveness, changes in sleeping patterns and disorientation in familiar places. Cats can also suffer from excessive night-time vocalization. Currently, it is not possible to stop or regress the progression of this disease and the treatments are designed solely to reduce the animal symptoms.

 

Equally, animals can suffer from a disease similar to Parkinson’s in the humans, characterized by tremors, difficulty in walking and balancing, muscle stiffness and slowness. Whist in humans this disease is more frequent in older people, in animals, this condition tends to affect mainly young animals. This is because in the animals, this is often a result of a hereditary condition, caused by a mutation in an important protein called dopamine. Dopamine is responsible to transmit the nervous signals, so once mutated, causes problems with the animal’s movement. Since all mammals produce dopamine, this condition can affect many species such as dogs, cats, horses, rabbits and monkeys. However, it is rare in older animals, because the majority of the species don’t live long enough to reach old age.

 

Finally, pets can also suffer from pathologies similar to the “multiple sclerosis” and “amyotrophic lateral sclerosis” in humans. In dogs, this is called “degenerative myelopathy” and is a genetic and progressive disease strongly associated with a mutation in a protein. Once mutated, the protein starts destroying the nerve cells, causing weakening of the hind limbs that can progress to total loss of limb function and incontinence. This pathology is most frequent in adult and large dogs, particularly breeds of Rotweiller, German Shepherd, Siberian Husky, Collie and Labrador, but it is rare in cats.

 

It is of paramount importance that the owners are aware and attentive to changes in behaviour and symptoms in their pets, to help dealing effectively with the problems that may arise from these pathologies, allowing a happier and healthier life.

 

Ricardo Ribas, PhD

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

Diabetes: Animals with sugary blood

Image from andremsantana in Pixabay.com

Diabetes is a very old disease, firstly described in records written back to the Egyptian times. It is a common but complex pathology characterized by the abnormal rise of the sugar levels in the blood. After eating, the food is broken down and converted into a type of sugar called glucose. Glucose is then transported by the blood to the different organs to be used as a source of energy by the cells. But for the glucose to get inside the cells it needs the help of a hormone called insulin. Insulin is produced in the pancreas and diabetes takes place when the pancreas loses the ability to produce insulin or when the cells fail to respond adequately to it. In both cases, glucose is not capable to enter the cells resulting in an abnormal accumulation and increase of the levels of glucose in the blood. Most importantly, and if not controlled, this can bring serious complications and can even result in death. 

There are two types of diabetes. The type 1, or insulin-dependent, occurs when the cells from the pancreas do not produce any insulin, whereas the type 2, also named as insulin-independent, occurs when either the cell from the pancreas produce a reduced amount of insulin or when the cells of the organism do not respond adequately to the hormone. 

But diabetes is not a pathology unique to humans. All mammals produce and need insulin to be able to carry glucose inside the cells, so diabetes can affect a broad range of animals, such as monkeys, pigs, sheep or horses. Nevertheless, dogs and cats are the most afflicted by the disease affecting as much as 1 in 100 animals. Not surprisingly, studies have suggested that the incidence of diabetes has been rising in recent decades. This is mainly the result of the recent rise in life expectancy as well as the increase of unhealthy lifestyles in pets due to their closer proximity with human. Changes in diet, obesity and reduced physical activity are increasing risk factors accounting for the recent surge in number of cases observed in pets.

However, just like in humans, genetics can also increase the risk of the animals to suffer from certain types of pancreatic and immunologic diseases. For example, in humans, type 1 diabetes tends to affect more frequently Europeans, particularly those from northern Europe, whereas black and Asian individuals are at lower risk of contracting the disease. Equally, animals of different breeds undergo distinct risks for the disease. For instance, dogs from breeds such as Samoiedo, Terrier, Schnauzer, Collie and Poodle, as well as the Burmese cats, are more likely to suffer from diabetes than Boxers, German Shepherds and Golden Retrievers, who present low risk. Sex also plays a major role. Whilst in dogs, the females are more susceptible to diabetes, in cats are the males the most affected. But it is not just in terms of sex that dogs and cats differ. Whilst almost all cases of diabetes in dogs are type 1; the vast majority of cases in cats are type 2 (80-95%), similarly to what happens with humans. 

It is therefore very important to raise the owner’s awareness for the symptoms of diabetes in their pets. Unfortunately, just like in humans, the symptoms of diabetes in animals is very unspecific, making it difficult to diagnose the disease. Animals often show an excessive increase in hunger, thirst and in the volume and frequency of urination together with weight loss. In more advanced cases animals can suffer from blindness caused by cataracts (characterised by opacity in the eyes). The sooner the diagnosis is made, the better the prognosis, but unfortunately, most owners are only aware of the condition when it is already at an advanced stage and hospitalization is usually the only option. Nonetheless, in most cases, once blood glucose levels are lowered, the animal can return home. Daily insulin injections as well as exercise and proper diet are generally effective measures to control the disease and prevent future complications. 

It is important to understand that once regulated and monitored, many diabetic animals can live a happy and healthy life. 

Diabetes in Normal and Natural Conditions  
Recent studies have shown that some animals can also use “diabetes” in normal and natural conditions. That seems to be the case for the Grizzly Bears. During spring, they respond normally to insulin to prevent the breakdown of the fat tissue, but once hibernation starts, their insulin stops working and they become insulin-resistant to allow the breakdown of their fat storages throughout the winter. Once hibernation terminates, the insulin recovers and restarts working normally. Similar mechanisms have been seen in dolphins indicating they can also make themselves resistant to insulin during periods of fasting being able to switch diabetes “on and off”. 

Ricardo Ribas, PhD 
Veterinary doctor, doctorate in veterinary sciences and researcher in the area of oncology

Animals with a Broken Heart!!

Image by Mohamed Hassan, pixabay.com

Cardiovascular diseases are pathologies that affect the heart and the blood vessels (veins, arteries or capillaries). Similarly to the humans, the incidence of these diseases has also been increasing in animals, as a result of the rise in life expectancy due to the advances in medicine.

The majority of cardiovascular diseases in dogs and cats are the result of old age, usually attributed to the natural aging of the heart and the blood vessels, but it can also be caused by injuries and infections. Examples include myocardial disease (weakening of the heart muscle), cardiac arrhythmias or valvular problems (characterised by the deterioration of the heart valves, preventing them to close properly). Nevertheless, cardiovascular diseases can also have a genetic origin. These are rare and tend to affect mainly younger individuals, often leading to further health issues and increased susceptibility to other diseases. 

Furthermore, the prevalence of these pathologies are not the same for all species. For instance, certain animals are resistant to a diet-induced blood vessel disease called atherosclerosis, characterised by the narrowing or blockade of arteries as a result of the buildup of fat, cholesterol or calcium. This shows the importance of the genetic component in some of these diseases. Similarly, the prevalence of some congenital heart malformations is also different between species. For example, it is known that the blood pressure is higher in giraffes and turkeys than in other species. Also some irregularities in the heart beating are normal and harmless in dogs, horses and moles but can have serious consequences in other animals. Moreover, incidences can also vary betwen breeds. For example, certain breeds of pigeons suffer from a higher incidence of atherosclerosis than others. Equally, some congenital heart diseases are known to be more common in purebred dogs, such as Boxers, German Shepherds and male Cocker Spaniels.

As well as in humans, animals can also live with heart disease for long periods without showing any symptoms, so early diagnosis is essential to delay their onset. Symptoms can emerge either slowly or suddenly after intense exercise, and in some occasions can be fatal. Dogs and cats are susceptible to heart disease at any age, so it is important that the owners are alert to symptoms such as tiredness, intolerance to exercise, dry cough, shortness of breath, weight loss, abdominal bloating or loss of consciousness (fainting) caused by the lack of blood reaching the brain. More rarely, animals can also show swelling of their legs, jaundice (yellow eyes, skin or mucous membranes) or coughing sometimes accompanied by blood. 

In addition to heart diseases, older animals are also be susceptible to pathologies affecting the blood vessels. For example, hypertension is a common problem in cats that suffer from hyperthyroidism or kidney disease and can lead to the formation of blood clots potentially resulting in cerebral ischemia, usually referred as stroke. Stroke happens when there is a disruption in blood supply to parts of the brain. This can lead to a variety of symptoms depending on the area of the brain affected as well as the severity of the incident. As well as in humans, animals can suffer from two types of stroke: ischemic (caused by reduced blood supply) or hemorrhagic (caused by accumulation of blood). Ischemic stroke occurs when a clot of blood or other material is lodged in a vessel, blocking the blood from reaching certain areas of the brain and leading to cell death. Hemorrhagic stroke is less common and occurs when a vessel ruptures, normally as a result of trauma or disease, damaging the cells due to excess blood inside the skull. The symptoms of stroke in pets are usually sudden but can vary depending on the location and the severity. It is therefore important for the owner to be alert to symptoms such as inability to move, incoordination, head tilt, abnormal eye movements, blindness, convulsions, loss of consciousness or behavioural changes.

In summary, the prevention of cardiovascular diseases is of paramount importance. Healthy eating and regular exercise are key to keep the animal in good physical condition. Furthermore, it is important that the owners are aware and attentive to any symptomatology the animal may present in order to allow an early detection and prevent problems that may arise, enabling a happier and healthier life. 

by Ricardo Ribas, PhD

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