An introductory survey of helminth control practices in South Africa and anthelmintic resistance on Thoroughbred stud farms in the Western Cape Province

Abstract

Fifty-one per cent of 110 questionnaires, designed for obtaining information on helminth control practices and management on Thoroughbred stud farms in South Africa, were completed by farmers during 2000. The number of horses per farm included in the questionnaire survey ranged from 15 to 410. Foals, yearlings and adult horses were treated with anthelmintics at a mean of 7.3+ / -3.0, 6.6+ / -2.7 and 5.3+ / -2.3 times per year, respectively. An average of 3.4 different drugs were used annually, with ivermectin being used by most farmers during 1997-2000. On 43% of farms the weights of horses were estimated by weigh band and 45% of farmers estimated visually, while both were used on 7% of farms and scales on the remaining 5%. Doses were based on average group weight on 50% of the farms and on individual weights on 46%. Forty-three per cent of farmers performed faecal egg count reduction tests (FECRT). Most farmers rotated horses between pastures and treated new horses at introduction. Faecal removal was practiced on 61% of farms and less than 50% of farmers used alternate grazing with ruminants. Faecal egg count reduction tests were done on 283 horses, using oxibendazole, ivermectin and moxidectin on 10, 9 and 5 farms, respectively, in the Western Cape Province during 2001. While the efficacy of oxibendazole was estimated by FECRT to range from 0-88% and moxidectin from 99-100%, ivermectin resulted in a 100% reduction in egg counts. Only cyathostome larvae were recovered from post-treatment faecal cultures

Effects of worm control practices examined by a combined faecal egg count and questionnaire survey on horse farms in Germany, Italy and the UK

“…In general, horses on Italian farms were treated less frequently with anthelmintics than those on German or UK farms. A differentiated management programme for different age groups was suggested as being a useful method providing adequate control [ 8 ] because young horses require more frequent treatment than adult horses [ 24 , 27 , 28 ]. As also observed within a recent similar study on German horse farms [ 29 ], the strongyle prevalence was lower in adults treated more frequently, while such an effect was not consistently found for the other two age groups.…”

“…Such an intensive treatment frequency should be a matter of concern, since a direct relationship has been shown between the frequency of treatment and the rate of AR development [ 6 , 26 , 30 , 31 ]. Additionally, an over-protective dosing strategy, while highly effective in the short term, will probably not be sustainable due to increasing development of AR [ 8 ]. Selection pressure for AR will be increased by treatment intervals as long as or even shorter than the prepatent period or the respective egg reappearance period [ 32 ].…”

“…Newly introduced horses should be treated with an effective, ideally larvicidal, anthelmintic drug or a combination of different anthelmintic drugs at arrival since they can introduce AR in a herd by harbouring anthelmintic resistant parasites [ 8 , 10 ]. It is also recommended to evaluate the success of any quarantine treatment to avoid introduction of resistant populations [ 11 ].…”

An evidence‐based approach to equine parasite control: It ain't the 60s anymore

“…In fact, several recent studies suggest that faecal analyses are minimally used, and instead total reliance is placed on frequent anthelmintic treatments (Anon 1998; Lloyd et al . 2000; Matthee et al . 2002; O'Meara and Mulcahy 2002).…”

Poor efficacy of the most commonly used anthelmintics in sport horse nematodes in Morocco in relation to resistance

“…The helminth control practices are not that much different from Europe (O'Meara & Mulcahy, 2002 in Ireland); the worming interval is somewhat larger (twice a year which represents 28 % of parasite control in Ireland) and the drug rotation is lower (rapid-59 % or annual-13 % of horse stables) in Morocco conditions. The intensity of treatments is also lower than that recorded in South Africa (Matthee et al, 2002), five times per year in adult horses; an average of 3.4 different drugs were used annually which is not the case in Morocco (one in most cases or two different drugs per year). Morocco is then a candidate for resistance in stud or leisure horses.…”