Seasonal changes of gastrointestinal nematode burden in sheep under an intensive grazing system

Uriarte, J.; Llorente, Mireia; Valderrábano, J.

doi:10.1016/j.vetpar.2003.07.030

Cited by 25 publications

(28 citation statements)

References 17 publications

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“…The worm burdens observed in this study (30 to 19333) were similar to values found (from 7364 to about 19193) in grazing sheep (Uriarte et al 2003). The wide variation among hosts has also been identified in Teladorsargia circumcincta parasitized sheep.…”

Section: Discussionsupporting

confidence: 89%

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Variability in the fecal egg count and the parasitic burden of hair sheep after grazing in nematode infected paddocks

2013

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Pesq. Vet. Bras. 33(4): 469-475, abril 2013 469 INTRODUCTIONThe frequent and continuous use of chemical anthelmintic drugs for deworming sheep flocks has resulted in the presence of lateral and multiple anthelmintic resistance in the parasites. This resistance leads to a concerning ineffectiveness of anthelmintics with large economic losses in sheep productivity (Coles et al. 2006, Papadopoulos 2008, Sargison 2011. Twenty-four countries have reported the presence of nematodes resistant to several anthelmintics (Jabbar et al. 2006). This situation has motivated workers around the world to search for alternative strategies to Variability in the fecal egg count and the parasitic burden of hair sheep after grazing in nematode infected paddocks 1Roberto González-Garduño 2 *, Pedro Mendoza-de Gives 3 and Glafiro Torres-Hernández 4ABSTRACT.-González-Garduño R., Mendoza- This study aimed to evaluate the variability in the fecal egg count (FEC) and the parasitic burden of naive hair sheep after grazing in nematode infected paddocks. The research was carried out in Tabasco, Mexico, during two periods (August and December). In each period 32 lambs were grazed for one month on African star grass (Cynodon plectostachyus) contaminated with gastrointestinal parasitic nematodes. FEC, packed cell volume (PCV) and body weight (BW) were recorded. Gastrointestinal worms were recovered at necropsy. Data were analyzed with the MIXED procedure of SAS using a model of repeated measurements over time. A higher number of Haemonchus contortus worms was found in December (2814±838) than in August (1166±305). The opposite occurred with Cooperia curticei (2167±393 and 3638±441, respectively). The FEC and correlation coefficient in respect to the worm burden were higher in December (6516 ± 1599, r=0.83, respectively) than in August (4364±771, r=0.44, respectively). A high variability in resistance-susceptibility to gastrointestinal nematodes (GIN) occurred in Katahdin × Pelibuey lambs after grazing.

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Section: Discussionsupporting

confidence: 89%

“…So, more generations of parasites were contaminating such paddocks. Similar results have been recorded in Spain and they are considered as a cause of increased infection in Aragonesa sheep (Uriarte et al 2003). However, environmental conditions could also affect the amount of parasites present in the pasture.…”

Section: Second Periodsupporting

confidence: 85%

Variability in the fecal egg count and the parasitic burden of hair sheep after grazing in nematode infected paddocks

2013

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“…In Section 3.1, the age-dependent rates λ(t) and η m (t) defining grazing strategies UM, TS and TM are inherently connected to the empirical data in [24] and Figure 2 of [22]. To be concrete, we first use the results in Section 3.2 of [20] to specify the function λ(t) for time instants t ∈ [0, τ] in scenario US and for time instants t ∈ [0, t 0 ] in grazing strategies UM, TS and TM.…”

Section: Empirical Data Age-dependent Rates and Resultsmentioning

confidence: 99%

“…In accordance with the empirical data in [22], resistance is not incorporated into modelling aspects since τ = 1 year is assumed in Section 3. The resulting models are thus related to the rotation of different anthelmintic classes on an annual basis, which has been widely promoted and adopted as a strategy to delay the development of anthelmintic resistance in nematode parasites; see, e.g., [12,13].…”

Section: Grazing Management Strategies: a Stochastic Within-host Modelmentioning

confidence: 99%

A Within-Host Stochastic Model for Nematode Infection

Gómez‐Corral

López‐García

2018

Mathematics

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Abstract:We propose a stochastic model for the development of gastrointestinal nematode infection in growing lambs under the assumption that nonhomogeneous Poisson processes govern the acquisition of parasites, the parasite-induced host mortality, the natural (no parasite-induced) host mortality and the death of parasites within the host. By means of considering a number of age-dependent birth and death processes with killing, we analyse the impact of grazing strategies that are defined in terms of an intervention instant t 0 , which might imply a move of the host to safe pasture and/or anthelmintic treatment. The efficacy and cost of each grazing strategy are defined in terms of the transient probabilities of the underlying stochastic processes, which are computed by means of Strang-Marchuk splitting techniques. Our model, calibrated with empirical data from Uriarte et al and Nasreen et al., regarding the seasonal presence of nematodes on pasture in temperate zones and anthelmintic efficacy, supports the use of dose-and-move strategies in temperate zones during summer and provides stochastic criteria for selecting the exact optimum time instant t 0 when these strategies should be applied.

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“…Para isto, é necessário conhecimento de fatores epidemiológicos variáveis em função do clima, das espécies de parasitas e hospedeiros, do tipo e da utilização da pastagem e de outros fatores ambientais (BARGER, 1999;URIARTE et al, 2003;EISKER et al, 2005). O principal fator climático regulador do ciclo dos nematódeos gastrintestinais em climas tropicais e subtropicais é a pluviometria, cuja elevação tende a aumentar a disponibilidade das larvas infectantes na pastagem (CATTO & UENO, 1981;SOUZA et al, 2000).…”

Section: Manejo Do Rebanho E Das Pastagensunclassified

Controle alternativo de nematódeos gastrintestinais dos ruminantes: atualidade e perspectivas

2008

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Seasonal changes of gastrointestinal nematode burden in sheep under an intensive grazing system

Cited by 25 publications

References 17 publications

Variability in the fecal egg count and the parasitic burden of hair sheep after grazing in nematode infected paddocks

Variability in the fecal egg count and the parasitic burden of hair sheep after grazing in nematode infected paddocks

A Within-Host Stochastic Model for Nematode Infection

Controle alternativo de nematódeos gastrintestinais dos ruminantes: atualidade e perspectivas

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