Hi everyone, I am glad to have you back. This week we are talking about something different from malaria. I will talk about man's best friend - the dog (Canis familiaris) and the parasites that affect his survival. It is known that most dog breeds rose recently within the last 200 years and have been artificially selected by humans. Because they have been domesticated for so long, they are so inbred that they are so vulnerable to many infections. Some of these infections are mild while others can be fatal. They are caused by different biological agents such as:
1) Bacteria
Under these pathogens, I will focus on Leptospirosis. This infection is caused by the Leptospira spirochete bacteria which is zoonotic, implying that it is transmissible between infected animals, other animals, and humans. The disease was first described by Adolf Weil in Germany while the parasite was discovered in 1915.
Symptoms include lethargy, increased thirst, high temperature, diarrhea, vomiting, jaundice, bloody vaginal discharge, and dark red speckled gums, just to mention a few. These typically come about when a dog gets in contact with urine from an infected animal that has been deposited in soil or water. Additionally, the chances of contracting the disease are increased by open sores on the skin. It is much more common in the tropics than in temperate areas. In a study that was conducted in Malaysia to determine the prevalence of Leptospirosis, it was discovered that of the 124 dogs that were tested, 53 (42.7%) were infected and of those 34% (18/53) died. In the United States alone, about 100-200 cases are reported every year. However, these infections and deaths can be avoided by giving anti-bacterial drugs such as penicillins for initial infections and tetracyclines for more advanced stages.
2) Fungi
Cryptococcosis is caused by the environmental yeast, Cryptococcus which is found in decaying vegetation (generally Eucalyptus trees) and droppings of birds. It is found in southern California, Canada, and is most prevalent in Australia. Dogs get infected when they sniff contaminated vegetation and bird poop. The symptoms include changes in behavior, seizures, blindness, nose bleeds, and so forth. The chances of recovery are very slim when the central nervous system is affected. In a published study, they observed that 52% of the dogs that were infected were killed. However, in less severe cases, this disease can be treated with antifungal medications such as miconazole or clotrimazole.
3) Viruses
Rabies is another zoonotic disease that is preventable with vaccines. However, if left untreated, it is 100% fatal. It is caused by the rabies virus (Rabies lyssavirus) and it is often transmitted by a rabid animal through a bite or infected saliva that comes in contact with a scratch, an open wound, or the mouth, nose, or eyes. Infected dogs often present with aggression, fever, excessive drooling, seizures, and so forth. Surveillance that was conducted in the States indicates that only 37 dogs were positive for rabies in 2020, which was 43.9% lower than in 2019.
The word rabies originates from the Sanskrit "rabhas" (to do violence) or the Latin "rabere" (to rage). In the past, the Greeks called rabies "lyssa" which means violence. Today, the rabies virus is classified in the genus Lyssavirus. The first recorded report of rabies killing dogs and humans can be found in the Mosaic Esmuna Code of Babylon in 2300 B.C. where if the dog transmitted rabies to another person, the Babylonians had to pay a fine.
Sources:
Abdul Rahman, M.S., Khor, K.H., Khairani-Bejo, S., Lau, S.F., Mazlan, M. and Roslan, M.A., 2021. Risk and Predictive Factors of Leptospirosis in Dogs Diagnosed with Kidney and/or Liver Disease in Selangor, Malaysia. Animals, 11(12), p.3405.
Gayathri, R., Archana, V. and Ramya, M., 2022. Molecular Diagnostic Methods for the Detection of Leptospirosis.
Ma, X., Bonaparte, S., Toro, M., Orciari, L.A., Gigante, C.M., Kirby, J.D., Chipman, R.B., Fehlner-Gardiner, C., Cedillo, V.G., Aréchiga-Ceballos, N. and Rao, A.K., 2022. Rabies surveillance in the United States during 2020. Journal of the American Veterinary Medical Association, 1(aop), pp.1-9.
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