New Tick-Transmitted Cattle Disease Now Confirmed in Kentucky

This past week, there were two cases of Theileria orientalis Ikedia, a protozoan disease, reported in Kentucky. The reports came from two cattle, one in Fleming County and the other in Hart County. This protozoon attacks red and white blood cells and causes bovine infectious anemia, lethargy, weakness, and possibly death in up to 5% of infected cattle. Cattle that recover can become carriers of the protozoan for the life of the animal. There is currently no vaccine or treatment for T. orientalis.

Figure 1. Asian longhorned ticks are small, only a few millimeters in length. They are a reddish-brown color but do not have many distinguishing features. The engorged tick is on the right and unfed tick to the left (Photo: Ric Bessin, UK).

Theileria is vectored by the Asian longhorned tick. This tick species has been confirmed in seven Kentucky counties: Boone, Breathitt, Floyd, Martin, Metcalfe, Madison, and Perry.  It is likely that other Kentucky counties may also be home for this species as it can be spread on birds and other wild animals.  Currently, the strategy is to monitor herds by regularly inspecting for ticks and to manage ticks as necessary. Once Asian longhorned tick is confirmed in an area, assume it is established, and management of this tick will be a continuing process that is focused on regular monitoring, animal treatments, and wildlife and habitat management.

Fortunately, this bovine disease is not a threat to human health. Humans cannot become sick from contact with infected animals or from consuming meat from affected animals, provided that the meat has been cooked to the appropriate temperature.

Management

Cattle producers can help to minimize Asian longhorned tick exposure risk by using the following management recommendations:

Monitor for Asian Longhorned Tick

Regularly inspect your cattle for ticks. When inspecting cattle, check on the head and neck, flanks and back, armpits, groin, and under the tail. Check cattle carefully as this is a small tick and can be overlooked easily. All three tick stages (larvae, nymphs, and adults) can be on the animals at the same time. When adding cattle to a herd, inspect purchased cattle for ticks and treat as needed before adding to the herd. Symptoms to monitor include lethargy, low weight gain, patchy hair, and signs of anemia. Consider having cattle with these symptoms tested by a vet if ticks are found on them. Submit collected ticks to the local county Extension office, which can help get the specimens to the Department of Entomology for identification.

Chemical Control of Ticks

Once they are found, consider chemical control of Asian longhorned tick from March into November as this is the potential period of high transmission. Combining multiple methods of control, such as ear tags, along with back rubbers and other devices, should be considered over this long period. Ear tags can provide long duration control particularly around the head and neck region, but the types of ear tags used need to be rotated regularly to reduce the development of insecticide resistance. For resistance management to be effective, products from chemical classes with different modes of action must be rotated. Be sure to read and follow all label instructions with ear tags, including the number per animal for tick control. Back and side rubbers charged with insecticide can be used in locations the cattle are forced to walk through daily. These devices need to be recharged regularly according to the respective pesticide labels. Pour-ons of ivermectin are used for heavy infestations of ticks and applied as a narrow strip along the topline of the animal. Increased numbers of pasture flies on treated animals after a heavy rain may indicate the need to retreat the animal. It is best to treat all animals in the herd at the same time and follow all label requirements including time to retreat, withdrawal periods, beef vs. dairy, lactating vs. dry, and use of personal protection equipment.

Habitat Modification

Ticks do not like to be exposed to the sun or low humidity, so tall grass and brush favors tick survival. Mowing pastures short reduces tick survival, so mow before rotating cattle into pastures even if the cattle have been treated for ticks. Keep in mind that these ticks can survive long periods without feeding. Additionally, wildlife in un-grazed pastures can also sustain tick populations. Exclude cattle from wooded areas as these areas are more prone to higher tick populations and wildlife levels.

Treating acreages with insecticides to manage ticks is not feasible or effective in most situations. Insecticides such as carbaryl or lambda-cyhalothrin can be applied to the edges of properties where habitat modification is not able to occur.

Acknowledgement

Management information adapted from: T. Dellinger, Eric Day. Managing the Asian Longhorned Tick: Checklist for Best Management Practices for Cattle Producers. Virginia Cooperative Extension.


By Ric Bessin and Jonathan Larson, Entomology Extension Specialists

Posted in Livestock Pests
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