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Dr. Elizabeth Martens, DVM Valleywide Veterinary Services, Bridport, VT
I saw my first tick 13 years ago in upstate New York. Now I routinely find them on myself after hikes and I keep up with flea and tick prevention on my dogs because Lyme and Anaplasma spread by ticks are found all too frequently sickening people’s pets these days. With a changing environment, most people have noticed ticks in quantities and places like never before. What does this mean for our cattle herds?
The good news is, Lyme disease is very unlikely to affect ruminants. So far, there has never been a case reported in cattle, sheep or goats and it appears that they are not susceptible to the bacteria.
There are several other diseases spread to cattle by ticks that we should be watching out for. Mycoplasma wenyonii, Anaplasma marginale and Theileria orientalis are all present and becoming more common in the Northeast every year. Look out for cattle with unexplained fever, lethargy, drop in milk production, anemia and jaundice (white to yellow mucus membranes – seen at the vulva, gums and conjunctiva).
These are blood borne diseases. Once an animal is infected and recovers, they remain a carrier and source of infection for other animals. This is important to keep in mind in terms of managing affected animals. It’s also a good reason to test sick animals for these diseases even if they look like they are going to recover on their own. A simple blood test can be done by most state veterinary laboratories and your veterinarian can advise on how to take and submit those samples. Anyone bringing cattle onto their property that have been south of Pennsylvania should inspect them for ticks and have them tested and quarantined before mixing with your herd.
Anaplasma and Theileria are rare enough that certain states will want any positive cases reported by your veterinarian. This record keeping won’t affect the farm at all, but is valuable for everyone to know how common the disease is by region and how quickly it is spreading. We should be watching for cases reported locally to decide about testing recommendation for farmers.
Anaplasma marginale is the most common tick transmitted disease in cattle worldwide and is no longer particularly rare in the Northeast. It is spread by ticks as well as biting flies, dirty needles, bloody castration and dehorning equipment and any other way of transmitting blood between animals. As always, clean needles should be used between animals, dehorning should be done as early as possible, and fly control should be a priority.
Most herds in the southern US are learning to manage cattle to live with Anaplasmosis. Exposure at an early age usually doesn’t cause severe disease and provides some immunity for life, while mature animals exposed for the first time and stressed animals can get very weak and die. A study of a dairy farm in Iowa showed that cattle testing positive for anaplasma produced significantly less milk than their negative herd mates – a loss of 5000 lbs of milk or more per cow per year.
Mycoplasma wenyonii has a really unique symptom of hindleg and udder or scrotal swelling, in addition to the more general fever, decreased milk production, swollen lymph nodes and anemia that lasts 2-5 days before the animal gets better. A recent study of farms in Wisconsin and Michigan showed that it is extremely common – in fact each of the 82 farms in their study had at least one cow that tested positive and on average about 72% of cows in the herds were positive. The economic and production level impacts of this bacteria are unknown.
In 2017, the Asian Longhorn Tick was first reported in New Jersey and has since been confirmed as far north as New York State, though it is reasonable to believe that it exists throughout New England. The Asian Longhorn tick is unique in that a single female can reproduce without a male present and create thousands of baby ticks very quickly. This tick often carries a new disease, known as Theileria orientalis genotype Ikeda. Theileria (pronounced tie-lehr-ee-uh) causes disease in cattle very similar to Anaplasma. Research out of New Zealand has shown that Theileria orientalis Ikeda causes significant economic losses to beef and dairy farmers – estimated at over $400 per cow.
Treatment options for these diseases are often unrewarding. Antibiotics and other supportive care will help sick animals survive, but there is no approved product that will clear an animal from being a carrier. Our best option is to prevent these diseases from being spread to this region and our farms for as long as possible.
Aside from hiring traveling bands of opossums and Guinea hens to eat ticks off pastures… there isn’t much I know of to reduce tick populations. Keeping grazing cows away from woods and border habitats will help reduce exposure. There is ongoing research on tick vaccines and organic compounds such as lavender oil that may be effective. Some regions utilize prescribed burning of pastureland and rotational grazing with poultry.
NODPA would like to thank Dr. Elizabeth Martens, DVM, Valleywide Veterinary Services, Bridport, VT for sharing her knowledge in this issue’s Ask The Vet column. Dr. Martens can be reached at https://www.valleywidevets.com/ or (802) 758-6888.