Worm control practices on sheep farms in Nyandarua District of Kenya

Contrasting views of animal healthcare providers on worm control practices for sheep and goats in an arid environment

A questionnaire survey was conducted to determine the worm control practices and anthelmintic usage of 150 key respondents involved in sheep and goat production in the arid Thal area of Pakistan. The information was collected by visiting farms, and interviewing the key respondents which included veterinary officers (n = 15), veterinary assistants (n = 51), traditional practitioners (n = 24), and small and large scale sheep/goat farm herders and owners (n = 60). Among all interviewed animal healthcare providers, the veterinary officers had the highest level of awareness of parasitic infection and advocated the use of modern available anthelmintics according to the predefined schedule. The farmers on the other hand, had the lowest level of knowledge about parasitic infections. They used modern anthelmintics at low frequencies (every six months) following an unusual practice of diluting the medicine. Veterinary assistants had a medium level of awareness about the parasitic infections using anthelmintic treatments when they deemed necessary rather than following a predefined treatment schedule. Traditional practitioners were also aware of parasitic infections and used traditional anthelmintics or a combination of the traditional and modern anthelmintics. The animal health providers had a different awareness and knowledge of parasitic infections which resulted in contrasting proposals for its' control. The farmers used worm control measures in accordance with their own views and those of animal healthcare advisors, combining modern and traditional treatments. This study provides the first insight into the differing views of those animal healthcare providers who form the basis for effective parasitic control within the sheep and goat industry of an arid region.

Feeding practices and effects of gastrointestinal parasite infections on live weight gain of small ruminants in smallholder mixed farms in Kenya

The objective of this study was to quantify the effects of gastrointestinal nematodosis on live weight gain (LWG) of sheep and goats kept in smallholder farms in Kenya. A total of 307 sheep and goats from smallholder farms were sampled using a 2-stage cluster and systematic random approach. Sampled farms were visited once a month for nine months during which a health and production survey questionnaire was administered, animals weighed and fecal samples taken for fecal egg count. Descriptive statistics and a generalized linear mixed model were performed in SAS. The mean LWG of suckling kids and lambs was low (mean=46 g/day). High fecal egg count and lack of feed supplementation were identified as the main factors limiting growth. Improved helminth control and nutrition are required to optimize production.

Accuracy of an anaemia scoring chart applied on goats in sub-humid Kenya and its potential for control of Haemonchus contortus infections

We tested the practical application of an anaemia scoring chart (the FAMACHA chart) as a method for controlling Haemonchus contortus in goats kept under smallholder conditions in a sub-humid area of Central Kenya. The objectives were: (1) to test the accuracy of the FAMACHA chart in identifying anaemic goats (PCV< or =18); (2) to quantify the proportion of goats left untreated at farm level when using the chart. On each of two farms, Small East African goats of various ages were allocated to two treatment groups; a FAMACHA group (F1 (n=34) and F2 (n=31) on farms 1 and 2, respectively) and a control group (C1 (n=34) and C2 (n=30)). In F1 and F2 goats with a FAMACHA score of 3, 4 or 5 were treated with anthelmintic after scoring. In C1 and C2 goats were treated every 4 weeks from 15 February to 20 July. Every 2 weeks all goats were scored with the FAMACHA chart and weighed. Furthermore, faecal samples were collected for faecal egg counts (FEC) and blood samples were collected for packed cell volume (PCV) determination. H. contortus was found to be the predominant nematode on both farms. The mean FECs were higher on farm 1 compared to farm 2, while in contrast the mean PCV levels were lowest on farm 2. The latter was most likely due to the presence of Fasciola spp., flea and tick infections on farm 2. The accuracy of the chart was evaluated by using PCV as the gold standard for anaemia (PCV< or =18%). The mean percentage of false-negative scorings per sampling was 0.7% on farm 1 and 1.6% on farm 2, while the mean percentage of false-positive scorings was 9.7% and 21.4%, respectively. It is most likely that the accuracy of the chart was negatively affected by the concurrent parasite infections on farm 2. The mean proportion of untreated goats per sampling was 89% and 77% on farm 1 and farm 2. It was concluded that the FAMACHA chart can be a valuable tool for decision-making in control of H. contortus in goats kept under smallholder conditions, without morbidity or mortality unacceptable to the farmer. The application may further reduce the risk of development of anthelmintic resistance by increasing refugia. However, caution should be taken under conditions where other anaemia-causing parasites are present (e.g. Fasciola spp. and ecto-parasites), since this possibly decreases the accuracy of the FAMACHA chart.

Worm control practices and anthelmintic usage in traditional and dairy cattle farms in the southern highlands of Tanzania

Worm control practices and anthelmintic usage in 177 cattle farms in Iringa district in the southern highlands of Tanzania was determined through a questionnaire survey. A total of 76 traditional, 92 small-scale dairy and 9 large-scale dairy cattle farms were included in the survey. Results indicated that 87.7% traditional, 97.8% small-scale dairy and 100% large-scale farmers relied solely on the use of anthelmintics, 2.7% traditional farmers used traditional medicines while 9.6% traditional farmers had not any form of worm control practice. Worm infection was ranked the second most important constraint of productivity in cattle in the three production systems. Most farms (57.6% traditional, 35.8% small-scale dairy, 66.7% large-scale dairy) used anthelmintics with a combination of levamisole and oxyclozanide. Benzimidazoles were used only in traditional (25.4%) and small-scale dairy (32.1%) farms while nitroxynil (Trodax) was mostly used in large-scale dairy farms (33.3%). Generally, 40% of farmers treated three or four times a year and the frequency in some farms was surprisingly high for resource poor small-scale farmers. The frequency of anthelmintic treatment was mostly the same regardless of the management system. Treatments in most farms depended on availability of money and drugs and not the epidemiology of parasites. A significant proportion (46.3%, P=0.007) of farmers especially in rural areas failed to follow their pre-planned treatment schedules due to lack of money (86%) and unavailability of drugs (6.6%). Many farmers (58.9%) had used the same type of anthelmintic for four or more consecutive years and 85.3% of them would continue with the same anthelmintic. Farmers in all management systems mostly purchased anthelmintics from private veterinary drug shops and about 43% traditional and 33.3% small-scale dairy farmers mostly in rural areas obtained anthelmintics from village extension officers. Despite the fact that all farmers were aware of worm infection and the associated signs in cattle, 42.5% had poor knowledge on the source of worm infection. Small-scale dairy farmers allowed only a 1-day withdraw period for milk regardless of the type of anthelmintic used and there was no milk and slaughter clearance in traditional farms. It was concluded from this study that worm control in Iringa faces serious constrains and that education of farmers and farm hands is not adequate. Moreover, poor quality control and high price of potent anthelmintics, few extension workers, low income and low education among farmers contributed significantly to erratic worm control practices and anthelmintic usage in peri-urban and rural areas.

Strategic use of moxidectin or closantel in combination with levamisole in the control of nematodes of sheep in the highlands of central Kenya

The strategic use of moxidectin or closantel in combination with levamisole (LEV) to control gastrointestinal nematodes of sheep in the highlands of central Kenya was examined. Thirty Corriedale female lambs aged between 6 and 8 months were assigned to three treatment groups of ten lambs each. The three groups of lambs were set stocked on separate paddocks for the entire study period of 12 months. Lambs in Group 1 were dewormed strategically with moxidectin at 0.2 mg/kg body weight and those in Group 2 with closantel at 10 mg/kg body weight together with LEV at 7.5 mg/kg body weight. These strategic treatments were given 3 weeks after the onset of both the short and long rains and at the end of the long rainy season. The third group of lambs remained untreated (control group). Nematode infections in the treated groups of lambs and larval infectivity for the pastures on which the lambs were grazing were well controlled compared with the untreated control group. This resulted in higher weight gains and packed cell volume (PCV) in the treated lambs compared with the untreated lambs. These parameters were comparable between the lambs treated with moxidectin and those treated with closantel plus LEV. The estimated monitory benefit per animal from the control of gastrointestinal nematodes using moxidectin or closantel in combination with LEV when compared with animals in the control group were US dollars 26 and 25, respectively. It was concluded that worm control strategies for sheep in the study area, which are based on anthelmintic treatments during the rainy seasons, are effective. Due to the extended period during which pastures remain infective in the high rainfall central highlands of Kenya, anthelmintics with sustained action such as moxidectin or closantel may be most effective. On farms where resistance to the commonly used benzimidazoles or LEV groups of anthelmintics has developed, moxidectin or closantel may be used in helminth control programs for sheep.

Effects of three anthelmintic treatment regimes against Fasciola and nematodes on the performance of ewes and lambs on pasture in the highlands of Kenya

The efficacy of strategic anthelmintic control of liver flukes (Fasciola) and gastrointestinal (GI) nematodes on the performance of ewes and lambs on pasture was assessed on a farm in the highlands of Kenya. In May 1999, 45 Corriedale ewes, aged between 2 and 3 years, were ear-tagged, weighed and allocated randomly to three equal treatment groups based on body weight. Faecal samples taken at this time revealed low levels of strongyle-type eggs per gram of faeces (EPG) and the presence of liver fluke eggs in only a few of the animals. All the animals were then set stocked for 12 months on separate paddocks in an area endemic for both Fasciola and GI nematodes. The ewes in group 1 were given a combined anthelmintic treatment against Fasciola and GI nematodes during the periods recommended for the control of Fasciola in the area (February, June and October). The ewes in group 2 were given the combined treatments 3 weeks after the onset of both the short and long rainy seasons (November and April, respectively). Those in group 3 were given separate treatments for Fasciola (February, June and October) and nematodes (3 weeks after the onset of the rainy seasons). The anthelmintic treatment against Fasciola consisted of triclabendazole at 10 mg per kg body weight, and that against nematodes was levamisole at 10 mg per kg body weight. The nematode EPG for the ewes in group 1 were higher than in groups 2 and 3 during both rainy seasons. The nematode EPG did not differ significantly between groups 2 and 3. The prevalence of Fasciola eggs (number of ewes shedding eggs in a group) in the ewes in groups I and 3 remained very low throughout the study period compared to those in group 2. The highest birth weights and the weight gains of lambs were recorded for the group of ewes given separate anthelmintic treatments for Fasciola and nematodes (group 3). The results of this trial indicated that, in an area like Nyandarua District, where liver flukes and GI nematodes are important constraints to sheep production, the best practice is to give separate treatments for the two groups of parasites at the recommended times.

Epidemiology of parasitic gastrointestinal nematode infections of ruminants on smallholder farms in central Kenya

In order to establish the infection pattern with gastrointestinal nematodes in ruminants in the central Kenya highlands, a study was carried out in 58 smallholder farms. The study involved monthly faecal examinations from sheep, goats and cattle and pasture sampling from eight communal grazing areas. Each month, six Dorper worm-free tracer lambs were introduced and four locally grazed cross-bred sheep were purchased for parasite recovery. The mean faecal egg counts (FEC) for cattle were low throughout the study period, whereas those for sheep and goats showed a seasonal pattern with high levels of infection occurring during the two main rainy seasons, especially in March, April and October. There were significant differences in egg counts over time and among farms. Haemonchus contortus was the most prevalent nematode in the tracer lambs whereas the previously exposed locally grazed sheep had significantly lower numbers of H contortus but significantly higher numbers of Trichostrongylus species The highest levels of infection in the tracer lambs occurred in November 1995 and January, May and June 1996. Based on this study, it is now possible to explore the possibility of using strategic treatments for the control of parasitic gastroenteritis in this area of Kenya.

Resistance to benzimidazoles and levamisole in nematode parasites of sheep in Nyandarua District of Kenya

The occurrence of anthelmintic resistance on 25 sheep farms in the Nyandarua District of Kenya was investigated, using the faecal egg count reduction test (FECRT), the egg hatch assay (EHA) and a larval development assay (LDA). In the FECRT, resistance to both benzimidazoles (BZs) and levamisole (LEV) was detected on four farms, resistance to LEV only on three farms and to BZs, only on two farms. Haemonchus contortus was the predominant nematode species in both pre-treatment and post-treatment faecal cultures. Out of the six farms where BZ resistance was detected in the FECRT, only isolates from one farm had an LD50 value higher than 0.5 microM thiabendazole (TBZ) (0.1 microgram TBZ/ml) in the EHA indicating resistance. Isolates from three other farms, where susceptibility to BZs was detected and four with suspected BZ resistance in the FECRT, had LD50 values higher than 0.5 microM TBZ in the EHA. The LD50 values for TBZ in the LDA for four of the six isolates with BZ resistance in the FECRT were higher than 0.5 microM (0.59-2.07) TBZ. There were disagreements in ascribing resistance for various farms, between methods of calculating and interpreting the faecal egg count reduction percentages (FECR%) based on the arithmetic mean, and those where the geometric mean eggs per gram (EPG) of faeces are used. Inclusion of pre-treatment EPG or control group EPG in the calculation of FECR% resulted in similar variations.