The ecology of infective larvae of bovine gastrointestinal trichostrongylids in dry season contaminated pastures in the Nigerian derived savanna

Abstract

Five experimental grass paddocks were sequentially contaminated with fresh bovine faeces containing known numbers of eggs of predominantly Haemonchus and Cooperia spp. during the 1984/85 dry season (November to March). Faecal, herbage and soil samples were examined at regular intervals between November and June in order to determine the rate of development and mortality of infective larvae (L3) in faeces, the pattern of herbage infestation with L3 and the role of faeces and soil as reservoirs of L3 during the dry season and early rains. L3 first appeared in faeces approximately 4 days post contamination (PC) and peak counts were obtained 28, 14, 7 and 14 days PC in the paddocks contaminated in December, January, February and March, respectively. The counts initially declined linearly at the rate of approximately 7535 L3/week and 10 947 L3/week in P2 and P4 respectively, due primarily to mortality but later there was an accelerated fall in the counts as the surviving L3 moved out of the faecal pads onto herbage. The overall trend of faecal larval populations in each paddock was therefore distinctly curvilinear. Although large numbers of L3 were present inside dry faecal pads in most paddocks throughout the dry season, none migrated on to herbage at that time of the year. Translation of L3 to herbage was very rapid and occurred simultaneously in all the paddocks 24 hours following the first heavy rainfall in late March. Consequently peak herbage infestations in all paddocks were coincident and occurred a few days after commencement of larval migration. The closer to the end of the dry season the contaminations were carried out, the larger were the subsequent early rains rise and the peak herbage infestation and the longer this infestation survived on herbage. No L3 were recovered from soil throughout the study, which suggests that faecal pads were the sole reservoir of L3 during the dry season and hence the source of the early rains herbage infestation.

The influence of water on the migration of infective trichostrongyloid larvae onto grass

“…present in the dung of cattle it has been shown that, once development is completed, L3 cannot escape once dung becomes desiccated (Williams and Bilkovich, 1973;Chiejina and Fakae, 1989;Agyei, 1997;Silva et al 2008). For Ostertagia, Haemonchus and Cooperia spp.…”

“…For Ostertagia, Haemonchus and Cooperia spp. present in the dung of cattle it has been shown that, once development is completed, L3 cannot escape once dung becomes desiccated (Williams and Bilkovich, 1973; Chiejina and Fakae, 1989; Agyei, 1997; Silva et al 2008). On dry, warm, days, cattle faeces, which are normally more liquid than sheep faeces and dropped in pats rather than in pellets, rapidly form a crust on the pat surface.…”

Controle biológico de nematóides gastrintestinais de caprinos em clima semi-árido pelo fungo Monacrosporium thaumasium

“…Na Nigéria, fezes de caprinos sofrem completa desidratação em 24 horas, na estação seca, e em 3 a 4 dias na estação chuvosa (Chiejina & Fakae, 1989). Tendo-se em vista a rápida dessecação das fezes de pequenos ruminantes, o período de maior disponibilidade de formas infectantes na pastagem é a época chuvosa.…”

Control sostenible de los nematodos gastrointestinales en rumiantes

“…Así mismo, en otro estudio dirigido a determinar la supervivencia de larvas de nematodos de vacas en una época seca de Australia, se observó que los mayores picos de larvas infectivas ocurrieron en épocas de lluvia, épocas precedidas de intensa sequía, porque, probablemente, el estiércol seco sirve de reservorio de larvas en épocas secas, y la reanudación de las lluvias favorece su traslación a los pastos (Barger, 1984). La misma observación fue reportada en los resultados de una investigación llevada a cabo en Nigeria (Chiejina, 1989). De esta manera, fue explicado un extenso brote de gastroenteritis parasitaria ocurrido en Australia en 1960, precedido de una época seca, donde el invierno desencadenó el incremento de larvas infectivas en las praderas.…”