Particularly when the mercury is well below zero (like it has been recently here in Ontario), many people dream of warmer places, and some of the luckier ones even get to jet off to regions closer to the equator to thaw out for a while. Before you set off for a tropical destination, it’s always good to do a little research so you know what you’re getting yourself into, which includes being familiar with local endemic diseases.
For today’s example, take African trypanosomiasis, also known as sleeping sickness. This disease is caused by a protozoal parasite called Trypanosoma brucei, which is transmitted by the bite of tsetse flies. The disease only occurs on the African continent, but it is endemic in 36 countries and poses a risk to approximately 50 million people. There are actually two subspecies of T. brucei that cause disease in man. Trypanosoma brucei gambiense tends to cause more chronic disease and has caused massive epidemics of sleeping sickness in the past. Trypanosoma brucei rhodesiense causes more acute disease, tends to occur sporadically and is more common in tourists and travellers in Eastern and Southern Africa. What a lot of people don’t realize is that T. brucei rhodesiense is actually a zoonosis – the main reservoir of the organism is livestock, whereas the main reservoir of the gambiense subspecies is infected people.
The World Health Organization (WHO) places human African trypanosomiasis (HAT) on its list of seven neglected endemic zoonoses. Some of the other disease on this list have also been discussed on the Worms&Germs blog, including rabies (one of our favorites), brucellosis and echinococcosis. In the early 1960s, efforts to control HAT brought the prevalence of the disease down to less than 1 case/10 000 people. Unfortunately, for a lot of reasons, the control efforts could not be sustained, and the African continent is now facing its third major epidemic of sleeping sickness. Better and ongoing surveillance, treatment of infected animal reservoirs, and control of the vector tsetse flies are all important components of the WHO’s control strategy for HAT on the African continent.
Dogs can be infected by both T. brucei gambiense and T. brucei rhodesiense, but they are not considered significant reservoirs of disease. Dogs may be more important as sentinels for human disease in endemic areas. There are, however, other Trypanosoma species that occur in dogs and people in North and South America, including T. cruzi, which causes American trypanosomiasis or Chagas’ disease.
More information about zoonotic sleeping sickness is available on the WHO website, and more information about Chagas’ disease in people is available on the CDC website. Keep watching the Worms&Germs blog for more posts about trypanosomiasis in pets.