Comparison of helminth and hard tick infestation between riding and work horses in Ahwaz, Iran

Abstract

Millions of dollars are spent every year for internal and external parasite control in horses; however, parasites remain one of the most important problems affecting their health and well-being (Raynaud et al. 1983). All horses have internal parasites and, if left untreated, ticks and worms can rob a horse of precious blood nutrients and energy. Problems associated with parasite infection include diarrhoea, colic, weight loss, poor growth, emaciation, impaired growth, predisposition to other infectious diseases and unexpected sudden death (Taylor et al. 2007). The common parasitic infestations of horses are caused by mange mites, lice, bots, ticks, roundworms, palisade worms, Trichonema and pinworms (Kingscote 1938). Ticks have eight legs (insects have six); non-engorged, they are small, flat and brown. Adult engorged ticks are dark blue-grey and the size of a pea. When they drop off, they leave behind a crater-like sore in the middle of an itchy/painful lump (George et al. 2002). Ticks are external parasites which suck blood from the host animal. Two general groups of ticks attack horses: hard ticks and soft ticks. Hard ticks have a long association with the host, feed slowly, take a large blood meal, drop from the host to moult and lay many eggs (Kaufman et al. 2009). The treatment of infected animals depends on the results of diagnostic tests, counts of eggs per gram of faeces (EPG) as well as methods for culturing, counting and identifying third-stage (L3) strongyle larvae per gram of faeces (LPG). For horses, such information does not exist in the published literature (Nielsen et al. 2010). A faecal egg count test is a microscopic examination for parasite eggs in fresh manure. This simple test can indicate which parasites are present and in what numbers. Adult parasites lay eggs or proglottids (portions of their bodies containing eggs) that pass out of the intestinal tract in the faeces. Internal parasite eggs can be detected in the faeces by performing a faecal egg count test. A faecal egg count test establishes the number of parasite eggs present in each gram of manure tested (EPG). Traditionally, a horse with an EPG value of 200 to 500 would be considered a candidate for treatment. In a herd, an average EPG value between all horses of 100 to 300 has long been considered the threshold between normal and unusual levels of parasite infestation (Evans and Rood 2009). Faecal worm egg counts, if conducted correctly, can also determine the general type of parasites present such as pinworms, threadworms, roundworms (Parascaris), strongyles and tapeworms. The Modified Wisconsin Sugar Flotation Method is highly sensitive for use with horses (three eggs per 1 g of sample) such that negative counts indicate the absence of adult parasites. Repeated negative information on the total number of worm eggs shed per pound of faeces can determine the rate by which an animal is re-contaminating its environment (Coates 2007). In the Ahwaz region, worm parasite infection is one of the most abundant animal diseases which cause economic losses and health problems for the infected animal husbandries. The aim of this study was to determine the prevalence of external and internal parasite infestation in about 120 horses in this region since little data exist in this field in Iran.