A stochastic model accommodating the FAMACHA© system for estimating worm burdens and associated risk factors in sheep naturally infected with Haemonchus contortus

Reynecke, D.P.; Wyk, J.A. Van; Gummow, Bruce; Dorny, Pierre; Boomker, Jacob Diederik Frederik

doi:10.1016/j.vetpar.2011.01.042

Cited by 8 publications

(5 citation statements)

References 19 publications

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“…Possible variations among breeds (Moors and Gauly, 2009), animal categories and ages (Mahieu et al, 2007), evaluators (Burke et al, 2007), management systems (Reynecke et al, 2011b), environments and facilities must be investigated to determine the real limitations of this method.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity and specificity of the FAMACHA© system in Suffolk sheep and crossbred Boer goats

Sotomaior

Rosalinski-Moraes

Costa

et al. 2012

Veterinary Parasitology

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Sheep and goats are the species of farm animal with the highest growth rate in Paraná State. The main problems facing Paraná State flocks are gastrointestinal parasites and anthelmintic resistance. One of the newest resources used to slow down the development of anthelmintic resistance is the FAMACHA © system, a selective method useful for controlling gastrointestinal verminosis in small ruminants. The purpose of the present research was to evaluate the sensitivity and specificity of the FAMACHA © system in sheep and goats and to compare the results for both species. The conjunctivae of 83 Suffolk ewes and 60 adult cross-bred Boer does were evaluated by the same trained person using the FAMACHA © system. The packed cell value (PCV) served as the gold standard for clinical FAMACHA © evaluation. To calculate the sensitivity and specificity of the FAMACHA © system, different criteria were adopted in turn: animals classified as FAMACHA © (F © ) 4 and 5, or 3, 4 and 5, were consid-ered to be anemic (positive test), and animals classified as F © 1, 2 and 3, or 1 and 2 were considered to be non-anemic (negative test). Three standard values of PCV, namely ≤19%, ≤18% or ≤15%, were used to confirm anemia. At all cut-off levels, the sensitivity increased if F © 3 animals were included as being anemic. However, changes in levels of sensitivity were associated with reciprocal changes in specificity. The sensitivity was higher for sheep than for goats, excepting when the criteria included PCV ≤ 18 and F © 3, F © 4 and F © 5 were considered positive. In contrast, the specificity was always lower in sheep for any criteria adopted. Other than in goats, using the ≤15 cut-off level for sheep, it is possible to opt not to drench the animals that were shown to be F © 3 because the sensitivity is still high, indicating that few animals that should have been drenched were overlooked. In goats, in contrast, the low sensitivity at all cut-off levels made it too risky to leave F © 3 animals undrenched. Even though the number of correct treatments for goats was always higher than that for sheep, the opposite was true for the kappa index for all the criteria tested. Therefore, the FAMACHA © system is suitable for the identification of anemic animals of both species. It is necessary that all small ruminants classified as FAMACHA © level 3 are also treated to increase the sensitivity of the method.

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Section: Introductionmentioning

confidence: 99%

Sensitivity and specificity of the FAMACHA© system in Suffolk sheep and crossbred Boer goats

Sotomaior

Rosalinski-Moraes

Costa

et al. 2012

Veterinary Parasitology

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“…The disadvantage of this technique is the possible presence of other parasites causing anemia or of nonparasitic causes of anemia. These difficulties have been studied with the aim of improving the system focusing on training and intervals for examinations (Reynecke et al, 2011b).…”

Section: The Famacha © Guidementioning

confidence: 99%

Challenges of nematode control in ruminants: Focus on Latin America

Molento

Fortes

Pondelek

et al. 2011

Veterinary Parasitology

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Gastrointestinal nematodes (GIN) of ruminants (cattle, sheep and goats) are ubiquitous and can cause severe injuries to infected animals and significant losses in farming revenues. GIN are able to survive severe environmental and host conditions, but mankind has developed a number of ingenious methods for parasite control. The commerce and use of modern anthelmintic drugs with a broad spectrum of activity has been a solid tool for nearly 40 years, however the continuous use of these drugs, has led to the selection of populations of drug-resistant worms worldwide. At present, the ever-growing agricultural systems in Latin America are facing many challenges and cannot rely on the far-reaching objective of parasitic elimination from the host or the environment. The lack of extensive programs for monitoring drug resistance exacerbates the negative consequences of reduced efficacy, which is evident in some areas with the increase in mortality rate even after treatment. Experts agree that new schemes of parasitic control are needed and should be based on the strategy of targeted selective treatment where affected hosts are identified and treated accordingly. In this article, we will focus our discussion on the challenges for the control of GIN in Latin America by 2020 imposed by reduced drug efficacy. We will evaluate phenotypic and molecular markers, methods for single-animal evaluation, and the implementation of schemes for anthelmintic treatment that address parasites in refugia.

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“…Resistance of gastro-intestinal parasites to anthelmintics has become more prevalent over the past years (Gray, 1991;Eady, 1995;Karlsson et al, 1995;Nieuwoudt et al, 2002) and is now at a very high level that threatens sustainable control and treatment of internal parasites Snyman et al, 2007;Reynecke et al, 2011). In addition, there has been growing concern that consumers demand animal products that are free from contamination of chemicals (Khusro et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Genetic parameters and relationships of faecal worm egg count with objectively measured wool traits in the Tygerhoek Merino flock

Matebesi-Ranthimo¹,

Cloete²,

Wyk³

et al. 2014

SA J. An. Sci.

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The costs of internal parasite control and treatment are potentially very high in grazing sheep. Faecal worm egg count (FEC) has been suggested as a suitable criterion for selection for resistance to nematode infestation in livestock. Genetic parameter estimates for FEC and its relationship with wool traits were assessed in the current study, using data from Merino sheep from a selection experiment maintained at Tygerhoek Research Farm. Data consisted of ~7 100 animals born between 1989 and 2010. Rectal faecal samples were taken from individual sheep at 13 to 16 months of age, after drenching had been withheld for at least 10 weeks, generally in July to September. Nematode eggs were counted with the McMaster technique, with a sensitivity of 100 eggs per gram of wet faeces. The fixed effects of birth type, sex, birth year and sex x birth year interaction were included in the operational model for FEC. Only the effect of additive animal affected the data for FEC. Heritability estimates of FEC ranged from 0.10 for untransformed FEC to 0.16 for Log (FEC + 100). The genetic relationships of Log (FEC + 100) with staple strength (SS), staple length (SL), coefficient of variation of fibre diameter (CVFD) and standard deviation of fibre diameter (SDFD) were favourable. The genetic correlations of FEC with wool weight traits were unfavourable in absolute terms, but not significantly different from zero. Selection for FEC is unlikely to result in unfavourable correlated responses to wool traits in South African Merinos, with the exception of wool weights. ______________________________________________________________________________________

show abstract

A stochastic model accommodating the FAMACHA© system for estimating worm burdens and associated risk factors in sheep naturally infected with Haemonchus contortus

Cited by 8 publications

References 19 publications

Sensitivity and specificity of the FAMACHA© system in Suffolk sheep and crossbred Boer goats

Sensitivity and specificity of the FAMACHA© system in Suffolk sheep and crossbred Boer goats

Challenges of nematode control in ruminants: Focus on Latin America

Genetic parameters and relationships of faecal worm egg count with objectively measured wool traits in the Tygerhoek Merino flock

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