June 2017 Articles

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Get Ready for Anaplasmosis Season Now

Get Ready for Anaplasmosis Season Now— Anaplasmosis is an economically important disease of cattle in Louisiana and many parts of the United States. Anaplasmosis is endemic in some parts of the Gulf Coast, meaning it occurs regularly and basically is “native” to the area. Increased movement of cattle due to drought, hurricanes, etc. has spread anaplasmosis to areas previously considered free of the disease. The implementation of the new Veterinary Feed Directive Rule (VFD) from the Food and Drug Administration in January, 2017 changed the status of the antibiotic used in feed or mineral to prevent anaplasmosis from over-the-counter to VFD. A VFD drug requires a veterinarian to prescribe use. There are requirements that must be met before a veterinarian can issue a VFD, so cattlemen should contact their veterinarian well in advance of vector season. Transmission — Anaplasmosis is caused by the blood parasite Anaplasma marginale. This organism infects red blood cells, which leads to anemia (“low blood count”). Anaplasmosis is transmitted by insects or people. Horseflies and some species of ticks are the main insect vectors. Spreading by other biting flies (such as stable flies), horn flies and mosquitoes is unlikely, but possible, during severe infestations.
People can spread anaplasmosis through reuse of needles and improper cleaning of instruments during dehorning, castration or tattooing. In one study, if a needle was used on an infected cow, the next animal had approximately a 60 percent chance of getting infected if the same needle was used. The incubation period from infection to clinical signs is 3-8 weeks. A typical scenario is a herd that is vaccinated and dewormed without changing needles to begin to show signs 3-8 weeks later. Clinical Disease — Cattle less than two years of age show no signs or only mild signs that may be confused with other diseases such as pneumonia. Cattle older than two years of age have more severe disease and are more likely to die. Animals that become infected usually are infected for life and become carriers of the disease. These carrier animals are immune to future disease with the same strain but become a source of infection for other cattle. Outbreaks usually occur in summer and fall but can occur anytime. Clinical Signs — Abortions may occur in females, and temporary infertility can occur in males. Animals with severe disease that live are likely to be “poor-doers” if they survive. Infected animals with less severe signs or no signs at all can have drops in milk production and infertility/embryonic death. This leads to decreased numbers of calves born and decreased weaning weights, both of which add to the financial losses due to anaplasmosis. In endemic areas, some herds may suffer the less-noticeable problems without having obvious illnesses and deaths. This makes the disease harder to recognize, but financial losses are still severe. Additional symptoms may include: · Fever· Weakness· Depressed attitude or aggression· Decreased appetite· Decreased milk production· White or yellow color to the gums or vulva, or yellow color to the whites of the eyes· Death Diagnosis — If anaplasmosis is suspected, producers should contact their veterinarians to confirm the diagnosis. Treatment — Whether or not to treat sick cattle and others in a herd that may be incubating the disease depends on many factors and should be discussed with a veterinarian. Prevention and Control — For herds in endemic areas there is constant potential for exposure, and total prevention or elimination of the disease from a herd is neither realistic nor recommended. The goal is to prevent and minimize clinical and subclinical disease and production losses. Producers in endemic areas should assume they have carrier animals in their herds that look perfectly healthy. These carriers are protected from severe clinical disease but can be a source of infection to other cattle. The following measures can help reduce the spread of anaplasmosis:· Do not reuse needles in animals older than 2 years of age, and clean equipment between each animal.· Supply tetracycline products in feed or mineral supplements – particularly during the seasons when disease outbreaks are most likely (summer and fall). Make sure the supplement is labeled for the “prevention of anaplasmosis.” It is illegal to use a product that is not labeled for anaplasmosis or to use a different dose from the one instructed on the product label. Purchase of these products now require a Veterinary Feed Directive from a veterinarian. · Control ticks and flies.· Vaccination. The only vaccine available is from University Products LLC (anaplasmosis.com). This vaccine is not recommended in all herds, but when the costs of deaths, chronic “poor-doers,” abortions and milk production decreases are considered, the vaccine may be cost-effective in herds in endemic areas. Vaccinate in early spring. Producers should talk to their veterinarians about cost-effectiveness of vaccination. In non-endemic areas, prevention of infection may be possible with biosecurity measures, especially testing of any animals added to the herd with the cELISA or PCR. Since this test may miss animals in the early incubation phase, single use needles, proper leaning of equipment and vector control are important in case a carrier slips into the herd undetected. Retesting these additions to the herd in six months to confirm their negative status also should be considered. Introducing cattle from non-endemic areas to endemic areas should be done carefully. If possible, introduce new animals during the seasons when disease spread is less likely. Also, consider vaccination on arrival. If vaccination is not available, a veterinarian can recommend antibiotic alternatives.— Dr. Christine Navarre, LSU AgCenter and School of Animal Sciences Veterinarian