Prevalence of Eimeria species among broiler chicks in Tabriz (Northwestern of Iran).

Abstract

Five chicks (2–6 weeks of age) were taken randomly from each of 218 broiler farms in Tabriz northwest of Iran. These chicks were submitted for post-mortem and parasitological examinations. Five Eimeria spp. were identified: E. acervulina, E. tenella, E. necatrix, E. maxima and E. mitis. The overall prevalence of Eimeria spp. among examined farms was 55.96 % (122 of 218 farms). E. acervulina was the most prevalent species (23.58%). Prevalences did not vary by flock size. Also, neither the use of coccidiostat nor previous coccidiosis clinical outbreaks were associated with the prevalence of infestation. The prevalence of infestation increased with the age of the chickens. Chickens with 5 weeks of age showed the highest prevalence of infestation. Coccidiosis is one of the most important and common diseases that affect poultry, it results in a great economic loss all over the world (Braunius, 1980). It is caused by the genus Eimeria of an Apicomplexa protozoan parasite (Shirley, 1995). This parasitic infection occurs in the epithelial cells of the intestine, despite the advances in nutrition, chemotherapy, management and genetics (Magner, 1991). Most Eimeria species affect birds between 3 and 18 weeks of age and can cause high mortality in young chicks (McDougald, & Mattiello, 1997). About 1800 Eimeria species affect the intestinal mucosa of different animals and birds (Shirley, 1995). In the domestic fowl Gallus gallus, nine Eimeria species are recognized: E. brunetti, E. maxima, E. necatrix and E. tenella are highly pathogenic, E. acervulina, E. mitis and E. mivati are rather less pathogenic, and E. praecox and E. hagani are regarded as the least pathogenic(Thebo, et al., 1988). Bad management (such as wet litter that encourages oocyst sporulation, contaminated drinkers and feeders, bad ventilation, and high stocking density) can exacerbate the clinical signs (Ruff, 1993). Coccidiosis can be controlled by good management including good ventilation, dry and clean litter (Jordan, 1995), cleaning and decontamination of drinkers and feeders (Gross, 1985), and proper stocking density in the farm (Jordan, 1995). We studied the prevalence of Eimeria spp. among broiler farms in northwest Iran. Also, we tested the risk factors of flock size, use of coccidiostats, and prior clinical coccidiosis. _____________Mun. Ent. Zool. Vol. 4, No. 1, January 2009__________ 54 MATERIALS AND METHODS Study site The survey was undertaking from September 2005 to December 2006 in 218 chicken farms. An average population of 5 000 000 broiler-chicks distributed over 500 chicken farms exists in this area. The houses of farms were built of brick and cement and are of different sizes. The method of housing the broilers is an intensive deep-litter system. Before birds were placed, the houses were cleaned, washed, disinfected and provided with new wood shavings. During the rearing period, the birds received mash feed. The broiler-chickens were slaughtered at an average of 48 days of age with an average live weight of 1.8 kg. The broilerchickens are produced in different broiler parent stocks and hatcheries in Iran. The most-common breed broiler was the Ross308. Sample size determination A sample of five birds per 10 000 is sufficient to diagnose coccidiosis (Mattiellio, 1990). Because the prevalence of coccidiosis in chicken farms in Iran has not been reported, the prevalence of infection in each farm was assumed to be 50%. The desired sample size was 218 houses (houses typically have <10 000 chickens each), using a 95% level of confidence and 5% desired absolute precision (Thrusfield, 1995). 218 chicken farms were randomly selected by using a random-numbers table; we also used such a table to select one house per farm. Randomly selected farms were initially contacted by veterinary services. Sampling Five chicks from each house were selected. The chicks were brought to the laboratory of parasitology in faculty of veterinary medicine in university of Tabriz for necropsy. All viscera were examined for gross pathological changes and the mucos of duodenum, jejunum, ileum and the caeci were examined for the presence of Eimeria spp. Stage according to the method described by Mattiellio (Mattiellio, 1990). Parasitological technique Wet smears of mucosa were prepared from intestinal and caecal scraping for microscopic examination of Eimeria spp. and Eimeria spp. identified according on the site of infection and oocysts morphology including size, color presence or absence of micropyle, cap and time of sporulation (Soulsby, 1982). Sporulation was performed in wet chamber at 24-26oC in a 2.5% aqueous solution of potassium dichromate (K2Cr2O7). At the same time that chicks were sampled, litter samples were collected for counting of oocysts in litter. A modification of the McMaster’s oocyst-counting technique was used (Soulsby, 1982). Litter samples were thoroughly homogenized by manual mixing. Then, a 9 g sample was weighed and soaked in 126 ml of water and allowed to stand overnight. Next morning, the samples were vigorously shaken to break up _____________Mun. Ent. Zool. Vol. 4, No. 1, January 2009__________ 55 the feces. Then, each sample was sieved through a tea strainer. The strained samples were poured into a 15 ml centrifuge tube. The tubes were centrifuged at 2000 rpm for 5 min. The supernatant fluid was decanted and sediment was mixed with a saturated solution of sugar in the centrifuge tube. The suspension was thoroughly mixed and a sample was taken and placed in a McMaster’s chamber. The number of oocysts within each ruled area, multiplied by 100 represents the number per gram of the original sample collected around the drinker and feeders of the same house from which chickens were collected on each farm. Data collection Information collected at the time of sampling included farmer’s name, address, farm location, flock age, flock size and use of coccidiostats in the feed for that flock and previous coccidiosis infection within the last year in the farm. Statistical analyses Data comparing prevalence by risk factors were analyzed using chi-square with a significance level of p<0.05. 95% confidence intervals were calculated for the prevalence.