A survey of the economic impact of subclinicalEimeriainfections in broiler chickens in Norway

Abstract

The objective of this work was to examine the impact of subclinical coccidial infection on commercial performance, expressed as a modified European Production Index, in broilers. Performance data, and litter and faecal samples, were collected from two independent observational surveys of Norwegian broilers receiving in-feed narasin during 2000 to 2004. Numbers of oocysts per gram (OPG) of litter collected during rearing (Study 1) or faecal samples collected at slaughter (both studies), and relative frequencies of Eimeria species categories (both studies) were calculated. Polymerase chain reaction-based identification of Eimeria species was performed in Study 2. A definition of flocks at risk of impaired performance associated with coccidia ("risk flock"), using the predominant species and OPG level as criteria, was tested. Coccidia had a significant effect on performance in the first, but not the second study. In Study 1 the following coccidia variables were found to be associated with impaired performance in multivariate models: OPG at slaughter (ordinal), mean OPG during rearing (ordinal) and "risk flock" (binomial). The European Production Index was approximately 9% lower in flocks with infection levels >50 000 OPG at slaughter in Study 1. The composition of coccidial populations shifted between Study 1 and Study 2, from a dominance of medium and large oocysts to a dominance of small oocysts. There was a substantial increase in prevalence of coccidial infection from Study 1 to Study 2, but mean infection levels were similar in the two surveys. The "risk flock" definition was useful as an indicator of coccidia-associated performance loss in Study 1, where subclinical coccidiosis was an important factor. The results suggest that the economic importance of subclinical coccidiosis may vary substantially with time, and they emphasize the need for population studies on the importance and dynamics of specific coccidial infections under different field conditions.

The economic impact of infection with Eimeria spp. in broiler farms from Romania

“…In Ethiopia, average total losses were estimated at 898.8 and 5,301.8 Ethiopian Birr per farm on small-and large-scale farms, respectively (Kinung'hi et al, 2004). Generally, it is assumed that 70% of the estimated costs are due to subclinical coccidiosis, by impact on weight gain and feed conversion rate (Gussem, 2007), and the economic importance of subclinical coccidiosis varies with composition of coccidial populations (Haug et al, 2008b).…”

“…The oocysts were washed free from the salt and potassium dichromate by repeated centrifugation and resuspended in tap water. After sporulation, oocysts were classified according to their size (Haug et al, 2008b), and virulence of each Eimeria spp. field isolate was assessed by lesion scoring (Johnson and Reid, 1970) following experimental infection.…”

“…Oocysts in each sample were classified according to the protocol described by Haug et al (2008b). Briefly, 50 oocysts from each sample were measured with CELL-F software using digital photographs (camera Olympus ODP72) taken with an Olympus BX61 microscope at 400x magnification (Long and Reid, 1982).…”

Loop-mediated Isothermal Amplification (LAMP) Assays for the Species-specific Detection of <em>Eimeria</em> that Infect Chickens

“…It is not currently possible to discriminate low level parasite escape from routine chemoprophylaxis or live vaccine replication from unchecked eimerian replication. Nonetheless, the technical ease of the protocol and definitive readout offers considerable improvement over the existing specialist and frequently subjective pathologyand morphology-led approaches 6,7 . Each assay may be completed at a cost of ~£0.75 per sample, independent of labour and equipment set up expenses.…”

“…Supplementary evidence can be gathered through microscopic detection of the environmentally resistant oocyst lifecycle stage in faecal or litter samples, although overlapping morphology can confound all but the expert 6,7 . Molecular alternatives using polymerase chain reaction (PCR), random amplification of polymorphic DNA PCR (RAPD-PCR) and quantitative PCR technologies have been available for up to 20 years [8][9][10] , but to date they have failed to become popular.…”