Prevalence And Intensity Of Infection With Gastrointestinal Parasites In Thomson’s Gazelles On Marula Ranch In Kenya
Thomson gazelles are an important part of wildlife in Kenya. Gastrointestinal (GIT) parasites may, however, be a limiting factor to their management. Gazelles also act as reservoir hosts for helminth infections, and any attempts to limit helminthosis in domestic ruminants in mixed grazing may be thwarted by the presence of the gazelles. Studies on the epidemiology of GIT parasites in wildlife in order to establish sustainable control strategies are therefore important. The objective of this study was therefore to determine the prevalence and intensity of infection with GIT parasites in Thomson’s gazelles on the ranch, in relation to weather factors, the age and sex of the host. The study was carried out in two phases. In phase I worm counts and nematode eggs per gram (epg) of feaces was determined. Rectal fecal samples were collected from gastrointestinal tracts of 6 and 19 male gazelles slaughtered at the ranch during the month of June and September 2003, respectively. Worms from the gastrointestinal tract were recovered and counted as described in the MAFF manual. Nematode eggs per gram (epg) of faeces, presence of fluke eggs, cestode eggs and coccidian oocysts was then determined. In phase II, 31 male and female gazelles (consisting of 3 young males, 6 young females 19 adult females and 3 male adults) were captured during the month of October 2003 and rectal fecal samples collected. Nematode epg, presence of fluke eggs, cestode eggs and coccidian oocysts were then determined from each sample. Strongyle-type nematode eggs were found in 23 out of the 25 (92%) slaughtered gazelles, while 9 (36%) and 8 (32%) gazelles, were shedding Trichuris eggs and coccidian oocysts, respectively. All the 31 captured gazelles were shedding Strongyle-type nematode eggs and coccidian oocysts. Trichuris eggs were found in 1 out of 3 fecal samples from the captured young males and in none of the samples from 6 captured young females and 22 adult gazelles. Mean Strongyle-type nematode epg for gazelles slaughtered in June and September were 497 and 2220 respectively, while that for the captured gazelles was 2672. This difference in mean epg between samples collected in June and September and October was statistically significant (p<0.05). There was a significant difference (p<0.05) in the mean epg for all 25 slaughtered males (1550) and the 19 captured adult females (3056). Fluke eggs and cestode eggs were not observed in any of the samples. Fecal cultures revealed predominance of Haemonchus, Gazellostrongylus and Trichostrongylus in fecal samples from the slaughtered gazelles and captured gazelles. Haemonchus, Gazellostrongylus and Trichostrongylus were isolated in the abomasa of 16 (64%), 17 (68%) and 9 (36%) of the 25 slaughtered gazelles, respectively. The mean worm burdens for Haemonchus were 10 with Standard deviation (Sd) of ± 16, 49 and Sd of ± 54 for gazelles slaughtered in June and September, respectively. The mean worm burdens for Gazellostrongylus was 100 with a Sd of ± 127, 25 and a Sd of ± 62 for gazelles slaughtered in June and September, respectively. The mean worm burdens for Trichostrongylus was 29 with Sd of ± 66, 26 and a Sd of ±51 for gazelles slaughtered in June and September, respectively. For Haemonchus and Trichostrongylus, the worm burdens were significantly higher (p<0.05) in guts collected in September than in June, while the reverse was true for Gazellostrongylus. Trichostrongylus, Cooperia and Nematodirus were isolated from the small intestines of 24 (96%), 15 (60%) and 5 (20%) of the gazelles, while Trichuris was isolated from the large intestines of all slaughtered gazelles. The Mean worm burdens for Trichostrongylus were 195 with a Sd ± 162, 852 and a Sd of ± 690 for gazelles slaughtered in June and September, respectively. The mean worm burdens for Nematodirus were 16 and a Sd of ± 27, 28 and a Sd of ± 120, for gazelles slaughtered in June and September, respectively. The mean worm burdens for Cooperia were 85 with a Sd of ± 127, 200 and a Sd of ± 220 for gazelles slaughtered in June and September, respectively. The worm burdens for Trichuris were 48 and a Sd of ± 24, 43 and a Sd of ± 40 for gazelles slaughtered in June and September, respectively. Worm burdens for Trichostrongylus were significantly higher (p<0.05) in September. In the abomasa of 13 of the 25 (52%) slaughtered gazelles, characteristic lesions were found. These consisted of nodules ranging in diameter from 3-4cm, which contained numerous adult male and female Gazellostrongylus worms and pus- like material. The worms were large in size protruding from orifices in the middle of the nodules. The worms were dark red in color, due to what appeared like blood ingested from the host. Correlation analysis was performed to determine the relationship between worm burdens and the fecal eggs counts and the relationship between the worm burdens and the weighs of the gazelles. Results showed that there was a negative correlation (-0.34) between the total worm burdens in the abomasums and the body weights of the gazelles, additionally there was a negative correlation (-0.2) between worm burdens and the fecal egg counts for gazelles slaughtered in June while there was a positive correlation (0.46) between worm burdens and fecal egg counts in those slaughtered in September. Results from this study indicate that GIT nematodes are prevalent in all age groups of Thomson gazelles on Marula Ranch during the dry and wet seasons. The egg counts were quite high with most of the gazelles having epg higher than 2000. Relatively high numbers of adult Trichostrongylus were recovered than any other species. Some of the predominant genera such as Haemonchus and Gazellostrongylus are voracious bloodsuckers, which poses a serious threat to the health and productivity of the gazelles. Haemonchus and other nematodes found in the gazelles are also transmissible to domestic ruminants on the ranch. Control of these parasites is therefore necessary.