Finding a vaccine for red mite.
Finding a vaccine for red mite.
Red mite is a pervasive pest in both the laying hen and broiler breeder sectors. It can cause significant production problems, act as a vector for disease and even increase mortality. Jake Davies reports from Scotland where research is underway to develop a vaccine.
The poultry red mite constitutes a substantial cost to laying hen production and there are few ways to control it. The pest can feed on up to 5% of a bird’s blood overnight, causing stress and anaemia, as well as lowering immunity and increasing mortality. The cost of red mite across Europe has been put at € 230 million in lost production every year. That stress can induce feather pecking, cannibalism and increased feed consumption. Besides this, red mite is known to carry diseases such as salmonella, E. coli and mycoplasmas. And it is pretty pervasive.
The red mite
Red mite live alongside many bird species but concentrated in the setting of a commercial poultry shed they can become a problem if populations are able to build up. New farms will often have a few months’ grace but the pest can be introduced by a wide range of things, such as people, pullets, egg trays or even carried in on wildlife. A mature adult will lay a clutch of eggs which takes about 2-3 days to hatch into larvae. From there, it is 1-2 days before they develop into protonymphs when they will take their first feed. Another 5 days and the mite is a fully grown adult, ready to lay eggs – and each female will lay up to 300 over her lifetime, demonstrating just how quickly populations can escalate. A normal infestation level could be up to 50,000 mites per hen and, in the case of a severe infestation, more than half a million mites per bird may be found in sheds.
Research into controlling red mite
Research suggests that about 90% of farms in most Western European countries are infested, with free-range and barn units thought to be more susceptible than colony farms. But control measures are limited, at least in Europe. Most farmers will re-purpose insecticides as acaricides, says Dr Alasdair Nisbet, head of the Vaccines Pillar at the Moredun Research Institute. “Some of the older classes of these, like organophosphates and spynosyns, were effective, but we’re starting to see resistance.” There is a single specific red mite deterrent active on the market that is proving to be effective, Dr Nisbet added, but it is not wise to rely too heavily on one product. This is what led to investigations of whether a vaccine might be an effective tool in controlling red mite. “Initially this was based around taking extracts of the mite and testing them to see if they were effective, that has since evolved into the development of a synthetic commercialisable vaccine for poultry red mite.”
Proof of principle
One of the first approaches was to take a simple extract of the parasite and inject that into hens. This generated antibodies in the hens which subsequently attacked mites when they fed on hens’ blood. In an experiment with the novel vaccine, 800 birds were split into 2 groups with half vaccinated and the other half free of red mite control. Red mite were introduced to the birds and after 4 months the vaccinated hens had 75% fewer red mites than those in the control group. “This demonstrated the proof of principle that we could control this parasite with a vaccine. It also opened the door to autogenous vaccines,” said Dr Nisbet.