Development, Survival and Availability of Gastrointestinal Nematodes of Sheep and Pastures in a Semi-arid Area of Kajiado District of Kenya

Abstract

A study was carried out on a ranch in the semi-arid area of Kajiado District in Kenya during the period July 2000 to June 2001 to determine the seasonal patterns of development and survival of gastrointestinal nematodes of sheep on pastures. A series of plots were contaminated with sheep faeces every month and pasture samples were collected weekly for the recovery and identification of larvae. The availability of infective larvae on naturally contaminated pastures was also monitored on the paddocks grazed by sheep and around the night pen and the watering point every month from July 2000 to June 2001. The results from the examination of the pasture samples indicated that rainfall distribution was the major factor governing the development and survival of the pre-parasitic stages. No parasitic larvae were detected from the plots contaminated during the dry months from July to October 2000, but development and translocation of infective larvae on pastures occurred on plots contaminated during the rainy seasons and soon after when relatively high moisture was present in the herbage (November 2000 to June 2001). During this period, peak larval counts occurred between the first and the second week post contamination, then declined to undetectable levels between week 4 and 16 post contamination. The lack of development of infective larvae during the dry season and the relatively rapid decline of their population during the wet season presents an opportunity for the use of pasture spelling as a means of helminth control in the study area. The availability of infective larvae on naturally contaminated pastures, around the night pen and around the watering point also followed the rainfall distribution pattern. Infective larvae were consistently recovered around the watering point throughout the study period. This indicated that the point is an important source of infection for sheep, especially during the dry season when other pastures are non-infective.

Risk factors of gastrointestinal nematode parasite infections in small ruminants kept in smallholder mixed farms in Kenya

“…The observed high number of animals with zero fecal egg counts is consistent with the expected FEC distribution (see for instance Polley, 1987) [15] in which only a few animals have high numbers of FEC and most present with no FEC in the fecal samples. The proportions of the genera of nematodes identified in the current study in which Trichostrongylus was the most prevalent and Oesophagostomum the least, is similar to findings of another study carried out in a semi-arid area of Kenya [7]. However, the order of prevalence reported by a study in Ghana was Haemonchus , Oesophagostomum , Trichostrongylus , and Cooperia [16]; while that of a study in South Africa was Haemonchus , Trichostrongylus , Ostertagia , Cooperia , and Oesophagostomum [17]; and that of a Zimbabwean study was Haemonchus , Oesophagostomum, Trichostrongylus , Ostertagia , Cooperia , and Trichuris [18].…”

Development and survival of Haemonchus contortus infective larvae derived from sheep faeces under sub-tropical conditions in the Potohar region of Pakistan

“…Other factors such as evapo-transpiration, soil moisture supply and type of vegetation can also influence survival and development, but these factors were not monitored. These results are consistent with those of other reports under tropical conditions (Banks et al 1990;Tembely 1998;Waruiru et al 1998) and in semi-arid area (Ng'ang'a et al 2004). The positive correlation of L 3 availability with rainfall and relative humidity is consistent with other reports that rainfall/moisture is an important factor in the development and translation of larvae to L 3 (Okon and Enyenihi 1977;Ndamukong and Ngone 1996;Agyei 1997).…”

“…Development, availability and longevity of free-living stages of H. contortus on pasture have been reported to follow seasonal fluctuations in tropical, sub-tropical and temperate regions of the world (Banks et al 1990;Besier and Dunsmore 1993a, b;Barger et al 1994;Agyei 1997;Tembely 1998). Larval development, survival and translocation of pre-parasitic stages on pastures at different times of the year provide knowledge about the critical risk period of the year (Barger 1999;Ng'ang'a et al 2004).…”

Helminths and Protozoa of the Gastrointestinal Tract of Ruminants in Tanzania

“…Most of the foregoing genera including Trichostrongylus, Oesophagostomum, Strongyloides, Bunostomum, Ostertagia and Toxocara have been shown to be present at various levels of prevalence in wild African buffalo Syncerus caffer in Ngorongoro and Arusha National Parks [26]. The nematode genera found in Tanzania have been reported in previous studies in neighbouring countries including Haemonchus, Trichostrongylus, Cooperia and Oesophagostomum in small ruminants in Kenya [27,28].…”

“…Temperature influences the development of nematode larvae: the optimal temperature for development of most trichostrongylid larvae is 22-30 C. Some trichstrongylid larvae such as T. colubriformis and O. columbianum are known to be resistant to desiccation, an ability that enables them to survive under extremely low or high temperatures [27,28]. Temperature and moisture are the main environmental variables that determine survival and development of coccidial oocyst to the infective stage.…”