The Hidden Danger: The Presence of Trypanosoma brucei gambiense in Sheep

Author: Angelina Akomea, BSc. Biochemistry, Cell, and Molecular Biology| University of Ghana

Imagine living in an African village, where the peaceful scenery hides a deadly threat that lurks in the shadows. You may have heard of African Trypanosomiasis, also known as sleeping sickness, a disease that can strike both humans and animals with devastating consequences. The culprit is a tiny parasite, called a trypanosome, that invades the bloodstream through the bite of a tsetse fly (Osório et al., 2008). For a long time, scientists believed that one subspecies of this parasite, trypanosoma brucei gambiense, only infected humans. But a recent discovery has turned this assumption upside down: this parasite has also been found in some domestic animals, especially sheep. This means that these animals can act as silent carriers of a ruthless enemy, making it harder to detect and control the disease. In this blog, we will explore the shocking discovery of trypanosoma brucei gambiense in sheep and its implications for disease eradication, revealing a hidden danger that requires our immediate action (Franco et al., 2014).

What are Trypanosomes and How Do They Cause Disease?

Trypanosomes are single-celled parasites belonging to the genus Trypanosoma, family Trypanosomatidae, order of Kinotoplastida, class Zoomastigophorea, and phylum Protozoa (Osório et al., 2008). They are able to establish infection by evading host-cell immunity. Notably, trypanosoma brucei gambiense and trypanosoma brucei rhodesiense are the most significant subspecies causing Human African Trypanosomiasis (HAT), or sleeping sickness  (Gutiérrez-López et al., 2015). HAT is a fatal disease affecting the nervous system and presenting symptoms such as fever, headache, confusion, sleep disturbances, and coma. Additionally, Animal African Trypanosomiasis (AAT), known as nagana, affects domestic animals, leading to anemia, weight loss, weakness, and eventually death (Cayla et al., 2019).

Image credit: Kateryna Kon/Shutterstock. Sleeping sickness parasites, 3D illustration. Trypanosoma parasites transmitted by tse-tse fly and causing African sleeping sickness.

How Do Trypanosomes Spread Between Hosts?

The complex life cycle of trypanosomes involves two hosts: a mammalian host and an insect vector, the tsetse fly (Steverding, 2008). When an infected tsetse fly bites a mammalian host, it injects infective forms of the parasite known as metacyclic trypomastigotes. Once in the bloodstream, these trypomastigotes multiply and transform into stumpy forms, poised to be ingested by another tsetse fly (Matthews, 2005). The transmission occurs when an uninfected fly feeds on an infected host, ingesting the stumpy trypomastigotes. Diagnosing trypanosomiasis is challenging due to nonspecific early-stage signs and symptoms. Laboratory tests such as microscopy, ELISA, DNA probes, and PCR aid in detecting the parasite (Agbo et al., 2001).

Why Is It So Hard to Control Trypanosomiasis?

Controlling trypanosomiasis presents numerous challenges due to the adaptability of trypanosomes. This adaptability complicates the development of effective control measures, as trypanosomes can change their surface coats to evade the host’s immune system or develop drug resistance (Urbina, 2001). Detecting and treating infections in animals is particularly challenging, as they can act as reservoirs for the parasite, especially when asymptomatic. Additionally, the distribution, behaviour, and feeding preferences of tsetse fly vectors further complicates control efforts. Furthermore, environmental and socioeconomic factors, including poverty, malnutrition, migration, conflict, climate change, deforestation, agriculture, and wildlife conservation, contribute to the prevalence and impact of trypanosomiasis (Luckins, 1992).

What Does the Discovery of Trypanosoma brucei gambiense in Sheep Mean for Disease Eradication?

One of the most significant findings in recent research is the presence of trypanosoma brucei gambiense in domestic animals, particularly sheep. Previously, this subspecies was thought to exclusively infect humans. However, the newfound ability to infect domestic animals suggests that they can serve as reservoirs for the parasite, intensifying eradication efforts (Franco et al., 2014). This finding has profound implications for disease control and eradication strategies. Efforts to combat African Trypanosomiasis must now address the expanded host range and the potential for inter-species transmission between animals and humans.

Final Words

The presence of Trypanosoma brucei gambiense in domestic animals, especially sheep, challenges assumptions and demands immediate action. This discovery expands the parasite’s host range, posing critical questions about disease control and eradication strategies (Franco et al., 2014). How can we effectively combat African Trypanosomiasis given this newfound reservoir? What comprehensive approaches can address parasite adaptability, reservoir hosts, tsetse fly behavior, and socioeconomic factors?

A multi-faceted approach is vital, integrating scientific research, community engagement, and cross-disciplinary collaboration (Cordon-Obras et al., 2010). By pooling resources, knowledge, and expertise, we can develop innovative interventions, raise awareness, and implement sustainable solutions. Let us unite in the fight against this hidden peril, striving to mitigate trypanosoma brucei gambiense’s impact on humans and animals in sub-Saharan Africa.

References:

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