Some observations on the epidemiology of Nematodirus battus in anglesey

Graham, EG; Harris, TJ; Ollerenshaw, C. B.

doi:10.1016/0168-1923(84)90082-0

Cited by 8 publications

(7 citation statements)

References 8 publications

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“…Nematodirus battus parasitizes the small intestine of ruminants, primarily sheep and can cause significant disease problems in grazing lambs in spring (Graham et al 1984; Thomas, 1991). Eggs shed by infected lambs generally develop over summer, receive a chilling stimulus over winter and hatch the following spring when temperatures increase above 11·5 °C (Van Dijk and Morgan, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…the size and timing of the larval peak in spring, but also the intensity of grazing of susceptible lambs at this time, which is mainly governed by the date of lambing, and hence, in most flocks, by autumn photoperiod (Smith and Thomas, 1972). Empirical studies aiming to explain variation in the timing and severity of infections between years (Graham et al 1984; Thomas, 1991; Van Dijk et al 2008; McMahon et al 2012) have focussed on temperature and taken no account of host availability. Since the lambing season is fairly consistent locally, the risk of disease is likely to change depending on the timing of larval emergence in relation to the age distribution of lambs, and hence their propensity to graze and ingest larvae (Smith and Thomas, 1972).…”

Section: Introductionmentioning

confidence: 99%

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Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming:Nematodirus battusin lambs as a case study

et al. 2015

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Mismatch in the phenology of trophically linked species as a result of climate warming has been shown to have far-reaching effects on animal communities, but implications for disease have so far received limited attention. This paper presents evidence suggestive of phenological asynchrony in a host-parasite system arising from climate change, with impacts on transmission. Diagnostic laboratory data on outbreaks of infection with the pathogenic nematode Nematodirus battus in sheep flocks in the UK were used to validate region-specific models of the effect of spring temperature on parasite transmission. The hatching of parasite eggs to produce infective larvae is driven by temperature, while the availability of susceptible hosts depends on lambing date, which is relatively insensitive to inter-annual variation in spring temperature. In southern areas and in warmer years, earlier emergence of infective larvae in spring was predicted, with decline through mortality before peak availability of susceptible lambs. Data confirmed model predictions, with fewer outbreaks recorded in those years and regions. Overlap between larval peaks and lamb availability was not reduced in northern areas, which experienced no decreases in the number of reported outbreaks. Results suggest that phenological asynchrony arising from climate warming may affect parasite transmission, with non-linear but predictable impacts on disease burden. Improved understanding of complex responses of host-parasite systems to climate change can contribute to effective adaptation of parasite control strategies.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming:Nematodirus battusin lambs as a case study

et al. 2015

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“…Hence, most eggs shed during the summer and autumn do not hatch until the following spring. Infective N battus larvae are generally thought not to survive for more than a few weeks on pasture (Thomas 1959, Gibson 1963, Boag and Thomas 1975, Graham and others 1984, Van Dijk and others 2010), being washed off the herbage by rainfall having exhausted their energy reserves to climb back up, or killed by ultraviolet light (Van Dijk and others 2009). Thus, the life cycle of N battus essentially involves transmission from one season's lamb crop to the next, and the accumulation of infection on pasture takes place over a period of grazing by susceptible lambs.…”

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confidence: 99%

Observations on the epidemiology of autumn nematodirosis in weaned lambs in a Scottish sheep flock

2012

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Nematodirosis was diagnosed in the south-east of Scotland during two consecutive autumns in lambs which were grazed on the same field. The problem was unpredicted based on the knowledge of the pasture and animal management, and rudimentary understanding of the behaviour of free-living stages of Nematodirus battus in the region. Unlike the epidemiology that has been described in the south of England, whereby autumn infection of lambs is believed to arise from autumn hatching of eggs shed during the previous spring without prior chilling, it is concluded that the autumn nematodirosis in a particular sheep flock in Scotland most likely arose following prolonged survival of larvae hatched during the spring from eggs shed during the previous summer, following periods of cold exposure over the previous winter. The infective larvae survived in large numbers in a small, sheltered strip of rough grazing, where they would have been protected from harmful ultraviolet radiation and heavy rainfall, before infecting lambs during the autumn. Understanding of the evolutionary potential, nematode parasites to adapt to changing environmental conditions depends on a thorough clinical investigative approach, and is a prerequisite for future preventive management.

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“…For Nematodirus species, in which eggs develop in the soil, water is also likely to play a role in the liberation of eggs from dung. Furthermore, rehydration of larvated eggs has been suggested to accelerate hatching, such that peaks in larval abundance on herbage, and risk of infection and disease, increase when rain follows a dry period (Graham et al , 1984; Haskell, 2008). However, this hypothesis has not been thoroughly examined.…”

Section: Introductionmentioning

confidence: 99%

The influence of water and humidity on the hatching of Nematodirus battus eggs

Dijk¹,

Morgan

2011

J. Helminthol.

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This paper examines the influence of water on the ecology of the eggs of Nematodirus battus, with a view to estimating the importance of including rainfall in mathematical models of parasite abundance. The literature suggests that, under pasture conditions, the availability of moisture is unlikely to be limiting for egg development, while eggs and infective larvae are highly resistant to desiccation. In the presented experiment, eggs that had been kept in salt sludges at 95% and 70% RH and were subsequently put at 15°C produced only a mildly accelerated, but not a mass, hatch, in the first few days after return to water. Eggs kept at higher osmotic pressures died. Mass hatching of infective larvae, described at pasture when spells of rain follow periods of drought, is unlikely to occur as the result of a sudden water influx into eggs. Since water is not necessary for migration of infective larvae from the soil on to grass, such peaks in larval abundance are more likely to arise from the effects of temperature on hatching of eggs.

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Some observations on the epidemiology of Nematodirus battus in anglesey

Cited by 8 publications

References 8 publications

Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming:Nematodirus battusin lambs as a case study

Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming:Nematodirus battusin lambs as a case study

Observations on the epidemiology of autumn nematodirosis in weaned lambs in a Scottish sheep flock

The influence of water and humidity on the hatching of Nematodirus battus eggs

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