Diversity of tsetse flies and trypanosome species circulating in the area of Lake Iro in southeastern Chad

Abstract

Background African trypanosomiases are vector-borne diseases that affect humans and livestock in sub-Saharan Africa. Although data have been collected on tsetse fauna as well as trypanosome infections in tsetse flies and mammals in foci of sleeping sickness in Chad, the situation of tsetse fly-transmitted trypanosomes remains unknown in several tsetse-infested areas of Chad. This study was designed to fill this epidemiological knowledge gap by determining the tsetse fauna as well as the trypanosomes infecting tsetse flies in the area of Lake Iro in southeastern Chad. Methods Tsetse flies were trapped along the Salamat River using biconical traps. The proboscis and tsetse body were removed from each fly. DNA was extracted from the proboscis using proteinase K and phosphate buffer and from the tsetse body using Chelex 5%. Tsetse flies were identified by amplifying and sequencing the cytochrome c oxydase I gene of each tsetse fly. Trypanosome species were detected by amplifying and sequencing the internal transcribed spacer 1 of infecting trypanosomes. Results A total of 617 tsetse flies were trapped; the apparent density of flies per trap per day was 2. 6. Of the trapped flies, 359 were randomly selected for the molecular identification and for the detection of infecting trypanosomes. Glossina morsitans submorsitans (96.1%) was the dominant tsetse fly species followed by G. fuscipes fuscipes (3.1%) and G. tachinoides (0.8%). Four trypanosome species, including Trypanosoma vivax, T. simiae, T. godfreyi and T. congolense savannah, were detected. Both single infection (56.7%) and mixed infections of trypanosomes (4.6%) were detected in G. m. submorsitans. The single infection included T. simiae (20.5%), T. congolense savannah (16.43%), T. vivax (11.7%) and T. godfreyi (9.8%). The trypanosome infection rate was 61.4% in G. m. submorsitans, 72.7% in G. f. fuscipes and 66.6% in G. tachinoides. Trypanosome infections were more prevalent in tsetse bodies (40.6%) than in the proboscis (16.3%). Conclusion This study revealed the presence of different tsetse species and a diversity of trypanosomes pathogenic to livestock in the area of Lake Iro. The results highlight the risks and constraints that animal African trypanosomiasis pose to livestock breeding and the importance of assessing trypanosome infections in livestock in this area.

Transmission of trypanosomiasis by tsetse flies in three active HAT foci of the Republic of Congo

“…This difference could result from the fact that, female live longer than males [4,32]. Similar ndings have been registered in Chad [30].…”

“…It is possible that the true infection rate could have been overestimated due to the fact that the whole mosquito was processed by PCR to detect infections. Studies conducted so far indicated different infection rate when screening the midgut, the proboscis, salivary glands or the whole body [23,30]. Moreover because detection of trypanosome DNA was used as a proof of active infection this could also have overestimated the infection rate since dead trypanosomes DNA could have been ampli ed this alongside other factors could have induced overestimation of the infection rate [31].…”

“…Factors in uencing trypanosome abundance and diversity in a given foci are still not well understood and deserve further investigations. The high infection rate of ies by different trypanosomes species are a proof of high vectorial competency of tsetse ies to different trypanosome species [30].…”

Parasite co-infection: an ecological, molecular and experimental perspective

“…Reflecting this, a large number of studies in different regions have reported the co-circulation of T. brucei , T. congolense and T. vivax , and these have been detected both in surveyed livestock and game animals [ 10 ], as well as in trapped tsetse flies (e.g. [ 11 , 12 ]). The major human infective Plasmodium species, Plasmodium falciparum , in contrast shows strict host specificity although other human infective malaria parasites, such as Plasmodium knowlesi , are more promiscuous and zoonotic.…”

Parasites and blood-meal hosts of the tsetse fly in Tanzania: a metagenomics study

“…The tsetse fly is also a vector of T. vivax , T. simiae , T.b. brucei , and T. congolense , all of which can cause trypanosomiasis in wild and domestic animals (AAT) [ 1 ]. HAT and AAT are severe and sometimes fatal diseases affecting the central nervous system in humans and the nervous system and muscles in animals, respectively.…”