Equines have long been among the most economically important livestock of Pakistan; however, their importance has decreased with the preamble of mechanization. The equines are renowned figure in mythology, art and ideals of religions. They have a significant role in agriculture, transportation and warfare. However, hundreds of diverse equine species were produced, allowing equines to be particular for definite tasks; light weight horses for riding and racing , miniature horses as pets, mules for pulling power and heavier breeds for farming. In some societies, equine milk and meat is taboo to consume but in some regions these are a source of food. In developed countries, horses are primarily kept for sports, leisure and pursuits, while in underdeveloped countries they are used as working animals.
In Pakistan, 1.5 million people are dependent on the equine population for their livelihood and agriculture. The usage of equines in rural and urban areas of Pakistan is increasing rapidly due to ever increasing energy crises and elevated fuel prices. In 1999-2000, there were about 3.8, 0.3, 0.2 million numbers of asses, horses and mules, respectively. This number reached over 4.8, 0.4 and 0.2, millions respectively in 2011-2012 which indicates an increasing trend of equine keeping in Pakistan over the past decades. Among the major threats of the equine health, gastrointestinal (GI) parasites mainly affect equines by inhibiting nourishment, anorexia, inadequacy in performance, mechanical obstruction of GI passage or compression of organs, weight loss, blood loss, debility, toxicosis, disease transmission other than parasitic diseases, facilitating secondary infection of bacteria, viruses and other microbial pathogens.
Equine GI parasitism is due to helminths and protozoa which are truly ubiquitous organisms. Worldwide studies on equines showed thriving helminths populations throughout a large range of different geographic and climatic circumstances. Wherever equines graze, the helminths species infect them. The GI parasites ova and cysts which are predominantly found in equines include: nematodes, trematodes, cestodes and protoza.
Nematodes (round worms) are the most important among GI helminths. In equines, large strongyles (red worms or blood worms), small strongyles (small worms), Parascaris equorum (ascarids), Strongyloides westeri, Habronema spp., Draschia spp., Oxyurides (pinworms), Dictyocaluc arnfieldi (lung worms) and Trichostrongylus axei (stomach worms) are responsible for nematodiasis.
Important members of cestodes which are responsible for equine cestodiasis include: Anoplocephala (A.) perfoliata, A. magna, Paranoplocephala mamillana and Moniezia (M.) pallida. Infection of these cestodes can occur following the eating of the infected intermediate hosts, the free-living mites. The first three members are more prevalent round the globe as compared to M. pallida. At the site of attachment, cestodes produce ulceration, severe erosions, induce hypertrophy of ileum and jejunum and rupture of duodenum.
Flukes (trematodes) are very uncommon and infrequently seen in equines. Flukes may be present in the GI tract or blood and are mildly pathogenic. Most prevalent species of trematodes are Dicrocolium dendriticum, Gastrodiscus aegyptiacus and Fasciola spp.
Worldwide prevalent species of protozoa of equines include Eimeria leuckarti, Giardia intestinalis and Cryptosporidium spp. All these infectious agents appear to have little clinical significance in equines; although, rare cases of diarrhoea have been reported in younger animals. Boots are the larvae of flies which reside in the stomach can cause ulceration through their migratory movements. Important species of Gasterophilus (G.) botfly include: G. nasalis, G. inerrmis and G. intestinalis, which are more abundant in equines.
Associated risk factors are those which are related to animal physical status and surroundings and make it more or less vulnerable to infection. Some factors include: type of pasture, breed, management practices, anthelmintics, anthelmatics resistance, seasonal variation, age, sex of animals, intermediate host presence, stoking density and immune status of animals which have been found to correlated its epidemiology of diseases in equines.
Evidently, economic impact of GI parasitism is observed on many fronts including poor performance and treatment cost. Therefore, indulgent of the parasitic health hazards and proper control methods for GI parasites are important to equines practitioners and owners.
Interval treatment approach to worm control was an old school for the GI parasitism control. The main principle of this programme was to administer anthelmintics to all equines in a short period of time to keep egg shedding as low as possible. Although, now obsolete but still the interval approach is being widely used by farmers and veterinary practitioners, which leads to permanent drug resistance. Which is a one way street with no U-turns.
Therefore; it is an ample need to adopt more sustainable methods for GI parasite control.
Eggs passed in faeces need a warm condition to hatch (broadly 6°C – 38°C, the optimum being around 25°) and it is otherwise once after hatching takes place. Recently, an epidemiological investigation was planned by the Department of Parasitology, University of Agriculture Faisalabad with technical collaboration of Brooke Hospital for Animals Faisalabad.
Rate of GI parasites infection is more in younger and older equines due to low immune status. Naturally, in young ones, ascarids are more prevalent as compared to other age groups. These ascarids are observed more resilient than other prevalent GI parasite of equines. So, it is recommended to keep different age groups (weanlings, yearlings, young, adult and older) separately and young ones and older animals should be treated against these GI parasites periodically. Pasture contamination has a big contribution to GI parasitic infection in equines of Pakistan.
Deworming should be done with more efficacious drugs e.g. ivermectin according to the prescribed schedule. The drug should be administered according to the exact measurement of equine body weight because administration of less than recommended dose, drug can lead to the development of resistance in parasites against the drug compound. Females are more prone to parasitic infection as compared to males due lactation and estrus periods, so special care is recommended for females. If equines are warned against GI parasitism into the stable/yard, treatment after every 3-4 months should suffice (maybe even less for low parasite egg-shedders).
However, in order to efficiently cover the area of GI parasites infections related to equines, professional collaboration of equine keepers and veterinarians may be required. For the diminution of the associated risk factor related to GI parasitism, an effective public educational campaign could also put in perspective.
The authors are associated with the Department of Parasitology, University of Agriculture, Faisalabad, Pakistan. The can be reached at <drurfabaig@gmail.com>