To improve our knowledge on the epidemiological status of HAT and AAT in the Malanga sleeping sickness focus, tsetse flies were trapped and the blood meal origins, as well as different species of trypanosomes, were identified in tsetse mid-guts. Glossina palpalis palpalis was the only tsetse fly species trapped in this focus, meaning that it is the main vector of the disease in this area. The high percentage of dead flies could be due to the high temperature observed during the dry season. In addition, the higher ADP may be another explanation. For instance, the average ADP observed during this study was about 7; indicating that more than 231 tsetse flies were trapped per day. This considerable number of flies trapped per day was difficult to dissect on the same day and some flies died overnight despite the fact that the tubes containing these flies were wrapped up in wet floor cloth.
The percentage (6.33%) of residual blood meals obtained here is higher than the values obtained (2.8% and 4.7%;  and , respectively) for the same tsetse species in southern Cameroon. The difference can be explained by the composition of the fauna as well as the number of domestic and wild animal species found in each focus. In the forest HAT focus of southern Cameroon where different wild animal species are found [19, 21], very few domestic animals (especially pigs) are bred. Therefore, tsetse flies may have difficulty taking blood meals due to the vivacity of wild animals compared to pigs and other domestic animals. In the Malanga focus where considerable numbers of pigs are found, wild animals are rare . Tsetse flies could easily take blood meals on domestic animals like pigs. This hypothesis is strengthened by the high percentage (58.3%) of pig blood meals found in tsetse flies from this focus. In the Malanga HAT focus, humans appeared as the second source of blood meals for tsetse flies, since about 33% of the blood meals were taken on humans; illustrating thus an important human/tsetse contact in this focus. Moreover, the identification of T. b. gambiense in the mid-gut of tsetse flies of this focus strengthens these human/tsetse contacts and suggests an active transmission HAT in the Malanga focus. This also suggests a transmission cycle including human and tsetse flies.
The results of the identification of different species of trypanosomes seem to indicate that the species-specific PCR method is more sensitive than the ITS, since 13 Trypanozoon infections were identified by specific PCR, whereas, only 4 of these infections were identified by ITS. These results are in line with those obtained by Desquenes et al.  who showed that a specific PCR method was more sensitive than the ITS in identifying different trypanosome species in African livestock. Using the ITS, different trypanosome species can be revealed with only two PCR rounds, because each trypanosome species will generate a DNA fragment with a specific molecular weight. As multiple infections are common in tsetse flies and mammals, this technique appears, therefore, very useful in large scale studies aiming to identify natural trypanosome infections. Despite the low sensitivity of ITS, this technique enables the identification of several trypanosomes species; allowing thus a reduction of the analysis costs. With this technique, a considerable number of samples can be analyzed in a reasonable time and different trypanosome infections can be revealed.
The low infection rate of T. brucei s.l. in tsetse flies of the Malanga focus is in line with results obtained by Makumyaviri et al.  who identified very few infections of this trypanosome in domestic animals of the same area more than twenty years ago. Eleven of the 13 T. brucei infections were due to T. b. gambiense, suggesting that most of the T. brucei s.l. infections found in this area were due to T. b. gambiense. These results indicate a current circulation of T. b. gambiense in the HAT focus of Malanga. Our results suggest very low transmission of T. b. brucei in this focus because only 8 tsetse flies were found with this infection. These results are in line with those obtained in animals where only one domestic animal was found infected with this parasite . The rarity of T. b. brucei in this zone can probably be explained by the fact that wild animals, known as being the reservoir of these parasites as well as the source of new infections, are scarce in this focus .
The identification of mixed infections involving different trypanosome species confirms previous results [6, 23–27], and reflects either the prevalence of such infections in vertebrate hosts of this area, or frequent feeding of tsetse flies on animals infected with different trypanosome species. However, the low percentage (7.02%) of mixed infections involving different trypanosome species does not corroborate results obtained in other African regions where a high prevalence of mixed infections has been reported in tsetse flies [6, 23–28]. The discrepancy between the percentages of mixed infections involving different trypanosome species can be explained by the availability of a suitable host for each trypanosome species. Despite the fact that the factors determining the distribution and abundance of trypanosomes are poorly known, it is likely, that most of these factors include the availability of suitable mammalian hosts . The presence of mixed infections of T. b. brucei and T. b. gambiense confirms results obtained in Cameroon where about 69% of T. b. gambiense mid-gut infections were mixed with T. b. brucei.
Among the trypanosomes of the subgenus Nannomonas, T. congolense was the most common species found, and T. congolense savannah type the most prevalent. These results are in line with those reported in Southern Africa . The high infection rate of trypanosomes belonging to Nannomonas, especially T. congolense, corroborates results obtained in tsetse flies of West, Central  and East Africa . This is in line with the results obtained in domestic animals of the same area . The high prevalence of T. congolense savannah type can be explained by geographical localization of the study area, which is located in the savannah zone.
The identification of different species of trypanosomes in tsetse of the Malanga HAT focus indicates the presence of trypanosomes causing HAT and AAT. Although the presence of T. b. gambiense in tsetse mid-guts is not proof of mature infection, since some mid-gut infections do not develop to maturation in the salivary glands, the identification of this parasite as well as the human blood meals in tsetse mid-guts indicates the circulation of T. b. gambiense between tsetse flies and man. This suggests an active transmission of HAT in the Malanga focus. Our results suggest that a flare up of the disease can occur at any time if control strategies are not put in place. This is of crucial importance for the HAT control program, especially at this moment in time, where active case detection is scarce in foci presenting low disease prevalence. The considerable number of pig blood meals associated with the identification of T. b. gambiense in tsetse mid-guts suggests that investigations on the animal reservoir of HAT at Malanga should be carried out.