Control of gastrointestinal parasitism with nematodes in dairy goats by treating the host category at risk

Abstract

-Infections of the gastrointestinal tract with parasitic nematodes remain one of the main limiting factors in grazing dairy goats. The usual mode of control of these parasitic diseases has up to now been based on the repeated use of anthelmintics. However, the prevalence rates of anthelmintic resistances, in particular to benzimidazoles, are now particularly high in the French dairy goat production. This situation makes it mandatory to reconsider the usual mode of control of these nematodes and to look for short term, alternative solutions which combine the control of gastrointestinal infections and management of anthelmintic resistances. One of the possible options is to leave a part of the flock without treatment during the grazing season in order to maintain alleles of susceptibility to anthelmintics within the worm populations. Previous epidemiological observations identifying the categories of host populations at risk are presented which provide the rationale for targeted applications of treatments. The results of assays on experimental flocks and from farm surveys examining the advantages and drawbacks of selective treatments are presented. The value of these results in combination with other alternative solutions of control are discussed in order to use minimum treatments with maximum benefits. dairy goat / anthelmintic / selective treatment / anthelmintic resistance / parasitic nematode Résumé -Maîtrise des strongyloses gastro intestinales chez les chèvres laitières par l'application de traitements ciblés. Les infestations par les nématodes du tractus gastro intestinal demeurent un des principaux facteurs limitant à l'élevage des chèvres laitières au pâturage. Le mode usuel de maîtrise de ce parasitisme reposait jusqu'à présent sur un usage répété de molécules anthelminthiques. Cependant, la prévalence des lignées résistantes aux anthelminthiques, en particulier aux benzimidazoles, en éle-vage caprin laitier en France, est désormais très élevée. Ce constat oblige à rechercher rapidement des 531

Sheep and goat nematode resistance to anthelmintics: pro and cons among breeding management factors

“…In conclusion, the most efficient way to limit the increase of anthelmintic resistance remains the reduction of the selection pressure by drugs, and optimal timing to maximise their efficacy. The treatment of the most probably infected hosts instead of the anthelmintic treatment of the whole herd [54,94] would keep a part of the parasite community from being submitted to selection pressure.…”

Managing helminths of ruminants in organic farming

“…This explains that the number of anthelmintic treatments is not enormously reduced in organic sheep farming [11]. The rational use of anthelmintic treatments on group or individual bases has been promoted [29,61] but is not yet in practice in conventional nor in organic farms. We are still in the need of efficient and low cost group/individual indicators for treatment, not only in organic farming but for all sustainable production systems.…”

“…Monthly monitoring of production (daily weight gains) and infection (average value of faecal egg counts) for determining the urge of all herd treatment have been proven efficient in controlling the infection of young meat cattle in Argentina [16]. The treatments may be applied selectively to the most susceptible group of hosts as proposed in dairy-goats [29] or to the individually most susceptible hosts in conditions where they can readily be identified [61]. Most of the indicators for gastrointestinal parasites are efficient for groups (faecal egg counts, plasma pepsinogen, or antibody response: [22]) but they remain poor on an individual basis.…”

Fatores de riscos associados à ocorrência de helmintos gastrintestinais em cabras leiteiras mantidas em sistema de pastejo

“…A variação sazonal da contagem de ovos nas fezes demonstrou que animais da raça Saanen são menos resistentes a helmintos gastrintestinais do que animais F1. Estes resultados corroboram estudos anteriormente realizados que observaram maior suscetibilidade à infecção Trichostrongyloidea em animais de raças puras de alto nível de produção leiteira LEVEQUE;DORCHIES, 2001, HOSTE et al, 2002b. Foi proposto que tal diferença de intensidade parasitaria poderia ser explicado pela demanda excessiva de nutrientes relacionados à alta produção de leite (COOP; KYRIAZAKIS, 1999).…”

“…Na maioria das fazendas, as fêmeas jovens, criadas para repor o plantel, são mantidas separadas dos demais animais, dificultando o contato prévio com helmintos e conseqüentemente o desenvolvimento de resistência. Em segundo lugar, a administração de tratamentos anti-helmínticos em caprinos baseiase normalmente em estimativa de peso médio , sendo que superestimação ocorre comumente para caprinos adultos enquanto que isto é menos provável em cabras de primeira lactação, cujo peso é geralmente mais leve (HOSTE et al, 2002b).…”