“Silent” circulation of Trypanosoma spp. in Tabanids (Diptera: Tabanidae) and Cattle in a Tsetse free Range land of Ngaoundere (Adamawa-Cameroon)

Abstract

The Adamawa region falls within the tsetse belt of Cameroon but harbours isolated pockets of tsetse free range lands like Ngaoundere. There is no report on the occurrence of tsetse and bovine trypanosomosis in Ngaoundere. To provide information on this subject, two Vavoua traps were used to trap vectors of bovine trypanosomiasis and at the same time, blood was collected from cattle. Genomic DNA was extracted from buffy coat of cattle blood (n=42) and biting flies (n=53). The nested PCR was used to screen the samples for Trypanosoma spp. During the 14 days of trapping in November and December 2017 in Ngaoundere, 127 flies were documented and classified under two taxa: Tabanidae and Stomoxyini. Three Trypanosoma spp. DNA was isolated from tabanid (18.9%) samples and identified as T. theileri, T. vivax and T. evansi and two of them that is T. theileri (4%) and T. vivax (3%) were also detected in cattle (7%). There was no case of trypanosome DNA isolated from all the screened Stomoxyini. This result indicates the “silent” transmission of T. theileri and T. vivax by tabanids in the absence of glossines in Ngaoundere.Keywords: Trypanosomes, tabanids, stomoxyini, PCR, Ngaoundere, Adamawa-Cameroon.

Spatial meta-analysis of the occurrence and distribution of tsetse-transmitted animal trypanosomiasis in Cameroon over the last 30 years

“…T. theileri is a non-pathogenic trypanosome that has mostly been encountered in ruminants, particularly cattle, sheep and goats. This species has been previously reported in livestock in Cameroon, especially in cattle from Adamawa and North regions [ 8 , 11 , 12 , 33 ]. The occurrence of T. theileri has also been detected in small ruminants, both goats and sheep, in neighbouring Gabon [ 81 ].…”

“…It is known that tsetse-transmitted AAT (TTAAT) extends in SSA over 10 million km 2 . Apart from its cyclical or biological transmission by tsetse flies, AAT can be mechanically transmitted through the infective bites of some dipterids, including Stomoxys and tabanids [10][11][12][13]. In the tsetse fly-free belts of tropical Africa, AAT exists in the apparent absence of tsetse flies, with transmission in these areas reported to be due to other dipterous flies and possibly hard-ticks carrying the parasite [14][15][16][17][18][19][20].…”

“…In the tsetse fly-free belts of tropical Africa, AAT exists in the apparent absence of tsetse flies, with transmission in these areas reported to be due to other dipterous flies and possibly hard-ticks carrying the parasite [14][15][16][17][18][19][20]. Cameroon is not exempt from non-tsetse-transmitted AAT (NTTAAT) as cattle in tsetse-free areas of Ngaoundere and the Far North region have been reported with trypanosome infections in the apparent absence of tsetse flies [11,12,21]. Furthermore, 4.02% of cattle from different ranches of tsetse-free Ngaoundere have been diagnosed with T. congolense and T. vivax [22].…”

“…Furthermore, 4.02% of cattle from different ranches of tsetse-free Ngaoundere have been diagnosed with T. congolense and T. vivax [ 22 ]. Tabanids, especially Chrysops longicornis , Haematopota decora and Tabanus taeniola caught from tsetse-free Ngaoundere, have been confirmed by molecular studies to harbour trypanosomes [ 11 ]. These reports indicate that biting flies could still sustain the transmission of AAT in the apparent absence of tsetse flies.…”

“…They are known to comprise 34 species and subspecies [ 24 ]. According to the technical report of the Special Mission for Tsetse fly Eradication (MSEG) of 2005 [ 11 ], 12 species of tsetse flies occurs in Cameroon including: (1) Fusca group including Glossina fusca congolensis , G. tabaniformis , G. nigrofusca , G. fuscipleuris , G. haningtoni ; (2) Palpalis group including G. palpalis palpalis , G. fuscipes fuscipes , G. tachinoides , G. caliginea , G. pallicera pallicera and (3) Morsitans group including G. morsitans submorsitans and G. longipalpalis .…”