Designing strategies for the control of coccidiosis in chickens on poultry farms using modern diagnostic tools

Abstract

Abstract:Coccidiosis is caused by the intracellular protozoan parasite Eimeria and is a major worldwide problem in the poultry industry today. The current strategies to control the disease still rely heavily on anticoccidial drugs and on the use of shuttle programs to periodically introduce attenuated live parasites onto poultry farms. Recently, because of the improved performance of broiler chickens, farmers are able to raise chickens for market within a period of only 5-6 weeks. This short growth period enables the development of strategies for coccidiosis control either by ensuring an even exposure of chickens to parasites in the litter, inducing immunity against reinfection, or by keeping parasite numbers below a threshold level wherein only subclinical infections will occur. Therefore, the development and use of new diagnostic tools to precisely identify the Eimeria species and strain and to measure the number of oocysts in the feces and litter can be very helpful in predicting exposure and designing strategies for the control of coccidiosis in the field. The purpose of this study was to describe recently developed methods of diagnosis in terms of their sensitivity and usefulness, describe ways in which litter oocyst numbers can be quantitated, and start to develop an analytical tool that can be used for designing strategies for the control of coccidiosis. A multiplex polymerase chain reaction-based assay has been developed that enables the identification of all seven Eimeria species in a single reaction tube. Previous reports have shown it is possible to detect one oocyst using a polymerase chain reaction-based assay; however, other reports have found that under both laboratory and field conditions the minimal level of sensitivity is only 20 oocysts. In addition, the present authors' studies have found that when using spiked mixed samples, the level of detection of a contaminating Eimeria species is only 5%. Therefore, it is imperative that a new method be developed with a tenfold higher level of sensitivity for field-testing. Once this test is developed and validated, it can be used to monitor the litter and assess the parameters (climate, hygiene, breed of chicken, etc) that govern coccidial outbreaks on farms.

Molecular Detection of Eimeria Zuernii in Cattle in Malang, East Java, Indonesia by Nested-PCR

“…Use of PCR has been hampered by characteristics of eimerian biology such as the oocyst wall's resilience to all but mechanical destruction, access to template DNA being restricted, and PCR being inhibited by the surrounding feces. Very few research has focused on the usability of these approaches for identifying Eimeria spp., despite the fact that various PCR tests have been developed to identify particular Eimeria species [13,24,25]. Using Eimeria oocysts enriched by flotation in saturated sugar and performing a freeze thaw 5 times to break up the oocyst walls greatly increased the sensitivity of the PCR [3].…”

“…It was observed that 20 oocysts of each species were insufficient for PCR-based species identification [3]. Although the test worked well with pure genomic DNA, it decreased a part of its sensitivity and variety of identification of species when used with the typical field samples [25]. Early identification of bovine Eimeria species is importance for effective control of clinical and subclinical eimeriosis.…”