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We live in an era where there is a high frequency of emerging and re-emerging infectious diseases. For the first time, we are witnessing an ongoing pandemic caused by a pathogen of zoonotic origin. COVID-19, caused by the Coronavirus SARS-Cov-2, is thought to have originated in bats and was amplified by an intermediate host with which humans came into contact at a wet market in Wuhan, China. Within months, COVID-19 caused nearly one million deaths and it remains a constant reminder of the risks posed by known and unknown zoonotic pathogens. Approximately two-thirds of emerging infectious disease affecting humans originate from wild and domestic animals. Thus, the risk of contact with disease-causing pathogens is higher in areas where wildlife interacts with livestock and humans such as wildlife conservation areas.
Our study aimed to investigate livestock as the potential bridge for zoonotic diseases at the wildlifelivestock interface at the interface of the Ruma National Park in Kenya. My supervisors, Drs Michael Okal and Shewit Kalayou, and I implemented a cross-sectional study with stratified one-stage cluster sampling for vector-borne disease pathogens in cattle. We sampled the blood of 680 zebu animals in 95 herds from six geospatial clusters within five kilometres of the Ruma National Park. The samples were screened for bacterial and protozoal pathogens by high-resolution melting analysis of PCR products. Together with our collaborators, we completed all analyses in the Martin Lüscher- Emerging infectious disease (ML-EID) Laboratory at the International Centre of insect physiology and Ecology. The lab offers an excellent facility for such studies and has been the focus of molecular biology studies advised by Drs Jandouwe Villiger and Dan Masiga.
Key findings
We detected several pathogens in the animals with more than 80% of all tested animals infected with Trypanosoma, Anaplasma or Theileria species. More than 50% of the animals bore a complex combination of pathogens with about 30% infected with diverse Trypanosoma species, including the zoonotic Trypanosoma brucei subspecies (7.5% prevalence). The area around Ruma National Park was a primary focus of human sleeping sickness in the 1960s. However, none of these tested positive for human-infective trypanosome species. Tickborne pathogens found included Anaplasma platys, a pathogen known to infect humans and dogs but without well-described pathogenesis.
For the first time, we showed that Anaplasma bovis affects cattle in the wildlife interface. Most, importantly, we found a new pathogen species (Anaplasma sp. Lambwe 1). We are currently implementing further studies to describe the infections and describe their relevance to human and animal health.
Over the last three years, since January 2017, we have collected over ten thousand samples of H. camelina off camels and camel blood in a cross-sectional study design. These samples were immediately preserved for transportation to Nairobi-based International Centre of Insect Physiology and Ecology (icipe) Molecular Biology laboratories for analysis. Trypanosomes and other pathogens are routinely studied through PCR-based assays and gene sequencing. We conducted experimental disease transmission studies through feeding assays by H. camelina on clean mice and rabbits.
Impact of the study
This study provides insight into the complexity of diseases pathogens in the interface with wildlife. The results could guide the development of livestock disease management strategies at the local and national level in addition to minimising the risks for zoonotic diseases. Importantly, it highlights the need for proactive surveillance of diseases, especially in the human-wildlife-livestock interface. Details of this study will be shortly available in peer-reviewed-journals.
