Lungworm disease in cattle will reach its peakduring August and farmers are urged to look out for the early signs beforesevere outbreaks occur. The August NADIS Parasite Forecast, sponsored by MerialAnimal Health, advises farmers to be vigilant for the early signs of husk,including coughing during periods of activity, a reduction in milk yield andloss of condition.
Early can appear as soon as one week afterinitial infection as the maturing larvae first reach the lungs. At this stagediagnosis is often based on clinical signs, since larvae will not be present inthe feces until they develop into egg laying adults approximately two weekslater. Once husk has been diagnosed immediate treatment of all cattle in thegroup is required to clear the infection and protect productivity.
Merial veterinary adviser, Sioned Timothy says:Young cattle during their first grazing season are most at risk from husk, butcases are increasingly seen in adults, so all ages of cattle should bemonitored for signs of disease.
As soon as signs are detected, its vital toseek advice from a vet or SQP. This will ensure appropriate investigation,diagnosis and treatment takes place as soon as possible.
Husk can be prevented either by vaccinatingbefore spring turnout or through strategic worming with suitable products.
Due to the unpredictable nature of husk aplanned approach to control is advisable. This should take into account localrisk factors such as climatic conditions and the farms own parasite status,and also address the risk posed by bought-in animals of unknown lungwormstatus.
The overall aim of control measures should be tominimize the risk of clinical disease, whilst allowing sufficient low-levelexposure to the parasite, promoting protective immunity. This can be a delicatebalancing act; too little exposure and they dont develop the immunityrequired, whilst too much will cause clinical disease and production losses. Tofurther complicate this situation, even immune cattle can succumb to severeclinical disease in the face of a high pasture larval challenge, highlightingthe need for on-going vigilance throughout the grazing season.
Many wormers used to treat gutworm (ostertagia ostertagii) such asEPRINEX (eprinomectin), will also treat lungworm. One treatment with EPRINEXwill clear lungworm and prevent reinfection for up to 28 days, with zero milkwithhold.
In sheep, there has been a reduced pasturelarval challenge due to the very dry weather experienced in many regions duringJune. However, the strategic use of safe grazing wherever possible to minimizethe parasite challenge faced by lambs, should play a crucial role in parasitecontrol programmes in the coming months.
After weaning, lambs moved to safe grazing maynot need to be wormed for up to six to ten weeks. However, this will depend onthe level of worm burden that the lambs are carrying when they are moved, thestocking rate, and weather conditions. Ongoing monitoring of worm burdens by fecalegg counts (FECs) on pooled samples from around ten lambs every seven to tendays can help identify whether a worm treatment is necessary.
Farmers should also consider adopting atargeted approach to wormer treatment whereby lambs are weighed and only thosethat are failing to grow at expected rates are dosed, says Ms. Timothy. Thisminimizes the number of unnecessary treatments administered, saving time andmoney and reduces the selection pressure for resistant strains of worm. Thereare other causes of reduced growth rate, such as cobalt deficiency, that may complicateinterpretation if not recognized and addressed, so advice should be sought froma vet or animal health advisor (SQP) before embarking on this approach.
Blow fly strike will continue to be a major riskduring August. Effective internal parasite control will minimize scouringand reduce the risk of strike. Following recent heavy rain, farmers should bealert to fly strike occurring on the back of sheep.
Strike prevention is the best form of control,says Ms. Timothy. Spray-on products containing insect growth regulators (IGRs)prevent infestations, but will not kill maggots that are already present.
Where sheep have already become struck, topicalproducts containing a synthetic pyrethroid (SP), or a diazinon based plunge dipwill treat the problem. These products may also provide protection against futureblowfly strike and treat other external parasites.
Farmers should consult their vet to ensure theyare using the most appropriate medicine for the circumstances, concluded Ms.Timothy.