Free-ranging pigs identified as a multi-reservoir of Trypanosoma brucei and Trypanosoma congolense in the Vavoua area, a historical sleeping sickness focus of Cote d'Ivoire

2021

Article référencé dans le Web of Science WOS:000733436300003

Traoré B. M., Koffi M., N'Djetchi M. K., Kaba D., Kaboré J., Ilboudo H., Ahouty B. A., Koné M., Coulibaly B., Konan T., Segard Adeline, Kouakou L., De Meeûs Thierry, Ravel Sophie, Solano Philippe, Bart Jean-Mathieu, Jamonneau Vincent

PLoS Neglected Tropical Diseases, 2021, 15 (12), p. e0010036 [19 p.] ISSN 1935-2735

Background The existence of an animal reservoir of Trypanosoma brucei gambiense (T. b. gambiense), the agent of human African trypanosomiasis (HAT), may compromise the interruption of transmission targeted by World Health Organization. The aim of this study was to investigate the presence of trypanosomes in pigs and people in the Vavoua HAT historical focus where cases were still diagnosed in the early 2010's. MethodsFor the human survey, we used the CATT, mini-anion exchange centrifugation technique and immune trypanolysis tests. For the animal survey, the buffy coat technique was also used as well as the PCR using Trypanosoma species specific, including the T. b. gambiense TgsGP detection using single round and nested PCRs, performed from animal blood samples and from strains isolated from subjects positive for parasitological investigations. ResultsNo HAT cases were detected among 345 people tested. A total of 167 pigs were investigated. Free-ranging pigs appeared significantly more infected than pigs in pen. Over 70% of free-ranging pigs were positive for CATT and parasitological investigations and 27-43% were positive to trypanolysis depending on the antigen used. T. brucei was the most prevalent species (57%) followed by T. congolense (24%). Blood sample extracted DNA of T. brucei positive subjects were negative to single round TgsGP PCR. However, 1/22 and 6/22 isolated strains were positive with single round and nested TgsGP PCRs, respectively. DiscussionFree-ranging pigs were identified as a multi-reservoir of T. brucei and/or T. congolense with mixed infections of different strains. This trypanosome diversity hinders the easy and direct detection of T. b. gambiense. We highlight the lack of tools to prove or exclude with certainty the presence of T. b. gambiense. This study once more highlights the need of technical improvements to explore the role of animals in the epidemiology of HAT. Author summarySignificant efforts to control human African trypanosomiasis (HAT) since the 1990's have drastically reduced the prevalence of the disease. Its elimination as a public health problem is being achieved. World Health Organization now targets the interruption of transmission for 2030. However, potential animal reservoirs of Trypanosoma brucei gambiense (T. b. gambiense), the main agent of HAT, may compromise this ambitious objective. It is the case in the Vavoua historical focus in Cote d'Ivoire where HAT cases were still diagnosed in the early 2010's. During a study conducted in this area, we scrutinized the trypanosomes circulating in pigs and people sharing the same environment using serological, immunological, parasitological and molecular tools. No HAT cases were detected. We showed that T. brucei s.l. and T. congolense actively circulated in free-ranging pigs. Even if no tools were sensitive and specific enough to unambiguously identify T. b. gambiense directly from biological samples, six isolated strains from pigs positive for trypanosomes were amplified for TgsGP, the only currently accepted T. b. gambiense specific molecular marker. The apparent discrepancies between the presence of T. b. gambiense in pigs despite the absence of human cases is discussed. These results stress the need for an efficient "molecular toolbox" to easily detect and identify T. b. gambiense in any animal it may infect.

Santé : généralités [050] ; Entomologie médicale / Parasitologie / Virologie [052] ; Sciences du monde animal [080]

COTE D'IVOIRE

Fonds IRD [F B010083877]

fdi:010083877