Trypanosomiasis in Dogs

Mechanical transmission can occur through biting flies and requires only that the blood containing infectious trypanosomes be transferred by bite from one animal to another. Trypanosomiasis is usually found in South and Central America, Mexico, and Southern United States. The response from the immune system is vigorous and produces inflammation, fever, lethargy and weight loss. Depending on the condition of your dog, the age, and how quickly the disease is diagnosed, treatment is difficult but some dogs continue to live a reasonable quality life. If advanced, this disease can affect your dog’s heart and other vital organs resulting in their failure.

Trypanosomiasis is transmitted to canines by infected insects (biting flies). Once parasites enter the cells in a dog’s body they multiply, rupturing the infected cells.

Acute symptoms to watch out for include:

• Depression -  your dog may seem disinterested in what is going on around him
• Lethargy - lacking energy and just wanting to sleep
• Your dog may have a fever 
• He may suffer from diarrhea
• Loss of appetite
• Enlarged liver or spleen – seen on tests or scans
• Neurologic abnormalities - he may suffer seizures
• Sudden death

With chronic symptoms, you may notice the following:

• Exercise intolerance with a reluctance to do anything active
• Increased heart rate (tachycardia)
• Abnormal heart rhythms such as skipping a beat or two
• Fluid accumulation throughout the body
• Coughing and finally death

Types  

Trypanosomiasis (T.) cruzi 

This is a species of parasitic euglenoid protozoan. They typically bore into tissue in another organism and feed on the blood or lymph. They are associated with heart disease in canines as the parasites attacks the heart muscle causing major damage. Infection occurs when the infected insect deposits it feces on your dog’s skin and then bite, causing an irritation and scratching. 

T. brucei  

This is a species of parasitic protozoan belonging to the genus Trypanosoma.  These species invade tissue and cause tissue damage to several organs and is also known as African sleeping sickness.

• The cause of disease comes from the bite of the tsetse fly which is carrying the trypanosomes, they act a biological vector (carrier of the parasite or disease)
• If an infected tsetse fly bites your dog, the parasites are transmitted in the saliva to the wound
• The insect also deposits infected feces on your pet’s skin and combined with the bite it aggravates the bite site causing irritation and scratching which only makes it worse by spreading the irritant around and pushing it into the open skin 
• Trypanosomes can also be spread by other various biting flies, for example, the horse flies (Tabanidae) 
• Mechanical vectors can include surgical instruments, needles, and syringes that have been contaminated with infected matter or flies landing on them

If you suspect anything is wrong with your dog, it always pays to have him checked by a veterinary expert. She will check for clinical signs and will want to know of any travel history to an endemic area where your dog may have been affected by trypanosomiasis. This disease is hard to pinpoint in the very early stages. The age of the dog and supporting observations (loss of weight, lethargy, fever, loss of limb control) all play a  part in diagnosis.

Some blood test smears may show infection if the parasite is in the aparasitemic phase, or they may be seen in the lymph nodes. The gold standard for diagnosis is a combination of clinical signs and a positive serology, which is done to detect the antibodies against the parasite. Diagnosis can be based on findings of congestive cardiac insufficiency in canines as the parasite often attacks the heart muscle.

Unfortunately, treatment for this condition is not easy, as it is hard to diagnose before it becomes advanced. The drug diminazene aceturate has been shown to be effective in some cases, but not all. In the United States, it is almost impossible to obtain this drug as it is not allowed in the country. The fact that this disease does not permit a definitive cure, and remains hard to eliminate means the prognosis is not good, but if diminazene aceturate works for your dog, then it offers a reasonable quality of life although there are neurological side effects to consider. 

Another drug that is available in the United States is nifurtimox and has been used in tests, but has serious neurological and gastrointestinal side effects for your dog. This condition also weakens your dog’s heart, so your pet may need additional medication to help, but the damage that has been done may shorten your dog’s life.  You will need to talk to your veterinary caregiver and decide what is the best solution for your pet.

There is no vaccination available to assist with the treatment or recovery. If your dog is diagnosed with this disease the prognosis is not good and although some treatment is available, it does not come without additional risks and side effects.  Recovery is long and needs to be monitored by your veterinary expert. Humans can be infected with the same disease, so care is needed regarding contaminated blood, as blood to blood contact could occur. Prevention remains the best management for this disease. Restricting contact to the carriers (biting flies) is essential. Insecticides may be used in and around where your dog is housed which will help, and your dog should never be allowed to eat the carcasses of potential disease carriers such as opossums, raccoons, and skunks.