Aspects of the bionomics of hematophagous symbovine dipterans in a hyper-infested rangeland of Ngaoundere (Adamawa-Cameroon)

A cattle exposure trial was carried out in an experimental cattle farm located in Galim near Ngaoundere. Observations were made from October–November 2016 and January 2017. Exposure commenced in the morning (8 h) and ended in the night (20h). The observed number of the different boophilic insect-groups was: Stomoxys (17,453), culicids (8925), Simulium (293), Chrysops (74) and Tabanus (34). Stomoxys (921.35) recorded the highest overall observed daily landing rate (ODLR) during the first survey-round (October–November 2016) and 740.85 during the second survey-round (January 2017) as compared to other hematophagous insect-groups observed. The preferred landing spots for most of the hematophagous insects were legs and belly regions, but Tabanus were also frequent around the head region. Brown colored cattle attracted Simulium, Chrysops, culicids and Stomoxys, but black animals were preferably attacked by tabanids. Cattle were mostly attacked in the overnight parks though there was no statistically significant difference (P?0.05). Two observed daily landing peaks (8 h–10 h and 16 h–18 h) were noticed for all biting fly-groups and was influenced by weather variables. The most frequent physical defense actions against landing flies by cattle was tail flicking. Such actions differed with survey-period, micro-ecosystems and color coat of cattle. Diurnal physical defense mechanism rhythms of cattle showed that head shaking was mostly used between 10 h–12 h and 16 h–18 h, but tail flicking and foot stamping only occurred between 13 h–15 h. There was a strong positive and significant correlation (r = 0.243, P < .001) in defense reactions and fly counts.