Sheep Scab Vaccine

Psoroptic mange (sheep scab) caused by infestation with Psoroptes ovis, is highly contagious, causes intense pruritus and is a major welfare and economic concern . Currently, disease control relies on chemotherapy; however issues with chemical residues, eco-toxicity and acaricide resistance have raised concerns about the sustainability of this strategy and alternative means of control are desperately needed . The concept of control by vaccination is supported by the demonstration of partial immunity in sheep following previous infestation with P. ovis : During primary infestation an initial “lag phase”, with small numbers of mites and tight, focal lesions, is followed by a more rapid “growth phase”, with increasing mite numbers and expanding lesions.

When this primary infestation is resolved (e.g. by treatment) and sheep are later re-infested, there is an extended lag phase, with lower mite numbers and reduced lesion sizes. Mite-specific IgG responses are similar in primary and secondary infestations but a more rapid induction of mite-specific IgE antibodies occurs in secondary infestations, suggesting that immediate hypersensitivity responses may contribute to immunity .

Description

A highly sensitive sheep scab test will enable farmers to differentiate between vaccinated and infested animals. The breakthrough is the result of Scottish research done by the Moredun Research Institute near Edinburgh and the James Hutton Institute, Dundee, which found a protein named Pso EIP-1. Moredun is currently developing a sheep scab vaccine and the new test will be phased in to support the vaccine, according to researchers.

Features of Sheep Scab Vaccine

We will assess the epidemiological benefits of additional control options, specifically the vaccine under current development at Moredun. In order to achieve this we will take a two-pronged approach:

  1. First we need to better understand the transmission dynamics of sheep scab. Transmission occurs through direct contact with an infested animal or by contact with contaminated fomites in an infested environment. Our current understanding of transmission of sheep scab within a flock is limited and may be influenced by a number of factors, i.e. stocking density, stage of disease in infested animals and the length of time of exposure to infested animals. We will develop and extend models of existing data from previous penned trials, which assessed within flock transmission of sheep scab to naïve animals following the introduction of infested “index” cases. The models will then be validated using penned trials (planned within RD2.2.6 Animal Disease Epidemiology of the Strategic Research Programme (SRP)).
  2. These models will then be used to better understand the degree of efficacy required by the sheep scab vaccine in order for it to have a significant impact on disease control. Finally, the models will be used to quantify the impact of vaccination against sheep scab transmission.

Treatment 

There are only two types of treatment available to treat or prevent sheep scab. They are plunge dipping with the organophosphate Diazinon (e.g. Osmonds Gold Fleece Sheep Dip and Paracide 62) or injecting with one of the macrocyclic lactones – moxidectin, doramectin or ivermectin (e.g. Cydectin, Dectomax, Ivomec).

Prices of Sheep Scab Vaccine

$56.00 – $69.99

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