Screening of Trypanosoma brucei gambiense in Domestic Livestock and Tsetse Flies from an Insular Endemic Focus (Luba, Equatorial Guinea)

Cordon-Obras, Carlos; García-Estébanez, Carmen; Ndong-Mabale, Nicolás; Abaga, Simón; Ndongo-Asumu, Pedro; Benito, Agustín; Cano, Jorge

doi:10.1371/journal.pntd.0000704

Cited by 28 publications

(33 citation statements)

References 33 publications

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“…Putting together results of T. b. gambiense infections in human and animals, it appears that the human-infective trypanosome was found in animals when the disease prevalence was high in humans. These observations contradict those of other HAT foci where T. b. gambiense was detected in animals of HAT foci showing low to very low disease prevalence [8,12,13]. The discrepancies between these results could be linked to animal species as well as the epidemiological patterns in each focus.…”

Section: This Hypothesis Is More Plausible With Previous Identificaticontrasting

confidence: 71%

“…Its direct impact is linked to the reduction of livestock productivity while the indirect impacts are associated with a reduced efficiency of draught animals for crop production [6,7]. Although several trypanosome species have been reported in domestic and wild animals residing within HAT foci in west and central Africa [8,9,10,11,12,13], equines have not been addressed thus far (mules, donkeys and horses). Indeed, the equine population is estimated to more than 127 million with approximately 85% in low income countries [14].…”

Section: Introductionmentioning

confidence: 99%

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Trypanosome infections in naturally infected horses and donkeys of three active sleeping sickness foci in the south of Chad

Vourchakbé¹,

Tiofack

Mbida

et al. 2020

Preprint

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Background Equine trypanosomiases are complex infectious diseases with overlapping clinical signs defined by their mode of transmission. Despite their economic impacts, these diseases have been neglected by the scientific community, the veterinary authorities and regulatory organizations. To fill the observed knowledge gap, we undertook the identification of different trypanosome species and subspecies naturally infecting horses and donkeys within the Chadian sleeping sickness focus. The end objective, being to investigate the potential role of these domestic animals as reservoirs of the human infective Trypanosoma brucei gambiense Method Blood samples were collected from 155 donkeys and 131 horses in three human African trypanosomiasis (HAT) foci of Chad. Rapid diagnostic test (RDT) and capillary tube centrifugation (CTC) test were used to search for trypanosome infections. DNA was extracted from each blood sample and different trypanosome species and subspecies were identified with molecular tools. Results From 286 blood samples collected, 54 (18.9%) and 36 (12.6%) were respectively positive for RDT and CTC. PCR revealed 194 (67.8%) animals with trypanosome infections. The kappa Cohen coefficients used to evaluate the concordance between the diagnostic methods were low; ranging from 0.087±0.04730 to 0.48 ± 0.06951. Trypanosomes of the subgenus Trypanozoon were the most prevalent (29.4%), followed by T. congolense forest (11.5%), T. congolense savannah (4.9%) and T. vivax (4.5%). Two donkeys and one horse from the Maro HAT focus were found with T. b. gambiense infections. Between animal species and HAT foci, no significant differences were observed in the infection rates of different trypanosomes. Conclusion This study revealed several trypanosome species and sub species in donkeys and horses, highlighting the existence of AAT in HAT foci of Chad. The identification of T. b. gambiense in donkeys and horses suggests considering these animals as potential reservoir for HAT in Chad. The presence of both human-infective and human non infective trypanosomes species highlights the need for developing joined control strategies for HAT and AAT.

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Section: This Hypothesis Is More Plausible With Previous Identificaticontrasting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Trypanosome infections in naturally infected horses and donkeys of three active sleeping sickness foci in the south of Chad

Vourchakbé¹,

Tiofack

Mbida

et al. 2020

Preprint

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“…Nevertheless, some data16,57,58 suggest the possible role played by asymptomatic human beings or animals as additional reservoirs. Asymptomatic individuals infected with trypanosomes who refused treatment and were followed-up for long periods (5–15 years) without showing any clinical manifestation of the disease have been described 59.…”

Section: Transmission Cyclementioning

confidence: 99%

Epidemiology of human African trypanosomiasis

Franco¹,

Simarro²,

Diarra³

et al. 2014

CLEP

259

230

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Human African trypanosomiasis (HAT), or sleeping sickness, is caused by Trypanosoma brucei gambiense, which is a chronic form of the disease present in western and central Africa, and by Trypanosoma brucei rhodesiense, which is an acute disease located in eastern and southern Africa. The rhodesiense form is a zoonosis, with the occasional infection of humans, but in the gambiense form, the human being is regarded as the main reservoir that plays a key role in the transmission cycle of the disease. The gambiense form currently assumes that 98% of the cases are declared; the Democratic Republic of the Congo is the most affected country, with more than 75% of the gambiense cases declared. The epidemiology of the disease is mediated by the interaction of the parasite (trypanosome) with the vectors (tsetse flies), as well as with the human and animal hosts within a particular environment. Related to these interactions, the disease is confined in spatially limited areas called “foci”, which are located in Sub-Saharan Africa, mainly in remote rural areas. The risk of contracting HAT is, therefore, determined by the possibility of contact of a human being with an infected tsetse fly. Epidemics of HAT were described at the beginning of the 20th century; intensive activities have been set up to confront the disease, and it was under control in the 1960s, with fewer than 5,000 cases reported in the whole continent. The disease resurged at the end of the 1990s, but renewed efforts from endemic countries, cooperation agencies, and nongovernmental organizations led by the World Health Organization succeeded to raise awareness and resources, while reinforcing national programs, reversing the trend of the cases reported, and bringing the disease under control again. In this context, sustainable elimination of the gambiense HAT, defined as the interruption of the transmission of the disease, was considered as a feasible target for 2030. Since rhodesiense HAT is a zoonosis, where the animal reservoir plays a key role, the interruption of the disease’s transmission is not deemed feasible.

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“…Such observations have given rise to the notion that T. b. gambiense does not spread in animal populations without the presence of humans. However, the parasite was recently detected in flies on Bioko [18], suggesting that there is ongoing circulation of the parasite, with the existence of a wild animal reservoir appearing plausible given the lack of detected cases in humans or domestic animals on Bioko. The existence of self-sustained cycles of infection in animals could jeopardise efforts towards gambiense HAT elimination.…”

Section: Introductionmentioning

confidence: 99%

Identifying Transmission Cycles at the Human-Animal Interface: The Role of Animal Reservoirs in Maintaining Gambiense Human African Trypanosomiasis

et al. 2013

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Many infections can be transmitted between animals and humans. The epidemiological roles of different species can vary from important reservoirs to dead-end hosts. Here, we present a method to identify transmission cycles in different combinations of species from field data. We used this method to synthesise epidemiological and ecological data from Bipindi, Cameroon, a historical focus of gambiense Human African Trypanosomiasis (HAT, sleeping sickness), a disease that has often been considered to be maintained mainly by humans. We estimated the basic reproduction number of gambiense HAT in Bipindi and evaluated the potential for transmission in the absence of human cases. We found that under the assumption of random mixing between vectors and hosts, gambiense HAT could not be maintained in this focus without the contribution of animals. This result remains robust under extensive sensitivity analysis. When using the distributions of species among habitats to estimate the amount of mixing between those species, we found indications for an independent transmission cycle in wild animals. Stochastic simulation of the system confirmed that unless vectors moved between species very rarely, reintroduction would usually occur shortly after elimination of the infection from human populations. This suggests that elimination strategies may have to be reconsidered as targeting human cases alone would be insufficient for control, and reintroduction from animal reservoirs would remain a threat. Our approach is broadly applicable and could reveal animal reservoirs critical to the control of other infectious diseases.

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Screening of Trypanosoma brucei gambiense in Domestic Livestock and Tsetse Flies from an Insular Endemic Focus (Luba, Equatorial Guinea)

Cited by 28 publications

References 33 publications

Trypanosome infections in naturally infected horses and donkeys of three active sleeping sickness foci in the south of Chad

Trypanosome infections in naturally infected horses and donkeys of three active sleeping sickness foci in the south of Chad

Epidemiology of human African trypanosomiasis

Identifying Transmission Cycles at the Human-Animal Interface: The Role of Animal Reservoirs in Maintaining Gambiense Human African Trypanosomiasis

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