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Lice Season is Approaching – Are You Ready?

When cold weather sets in, many cattle producers can take a sigh of relief as fly season draws to a close. However, the winter doesn’t herald complete freedom from external parasite concerns. It’s only starting for cattle lice.

Winter – the season of the louse

While always present on cattle, these opportunistic parasites spend the summer months laying low and not reproducing.  Because they are sensitive to sunlight, they tend to hide in dark places on the underside of an animal’s body, and especially when the haircoat is short and provides no protection. Lice take advantage of the cooler weather, shorter days, and longer hair coats to start laying eggs and wreaking havoc.

Lice emerge from their hiding places (folds of skin, mainly) as the hair coat increases in length, usually around late October into November and December. They can inhabit any part of an animal, but they seem particularly bothersome on the neck, shoulder, back and topline.

Consequences of uncontrolled lice infestation

Even though small numbers of lice are always present on healthy cattle, they are also opportunistic and will take advantage of cattle that are experiencing abnormal levels of stress. This stress may come from weather extremes, nutritional deficiencies, or other factors. Typically, a stressed animal will have higher levels of blood cortisol, the stress hormone that, in larger amounts, will cause a decrease in appetite and immune suppression.

A weakened immune system opens an animal up to a number of potential problems, external parasites being just one of them. Even in normally healthy animals, a significant lice infestation can have detrimental effects to their ongoing health.

Cattle that are experiencing the uncomfortable symptoms of lice will spend the majority of their time attempting to relieve the itching, taking them away from their number one job: eating. This can have dire consequences, considering their rumen health is dependent on a steady intake to function properly.

Some of the most significant effects an infestation can have include:

  • Reduced feed intake
  • Shrink
  • Higher susceptibility to infection
  • Cold stress (from rubbing off protective hair coat)
  • Reduced milk quality and production in cows (especially important for those fall calves)

Symptoms of lice infestation

The signs of lice infestation often manifest with animals rubbing, scratching and licking various areas on their bodies. Fence lines may be the first indicator of a problem, with tufts of scratched-off hair deposited in the barbs. Upon closer inspection of the animals themselves, there may be areas of raw, abraded skin or even crusted-over patches. When the itching becomes severe enough, they may even rub the majority of their winter coats off, leaving them susceptible to cold stress.

Cattle with severe infestations will also lose weight, as they are occupied with trying to relieve the irritation caused by the biting and chewing of these parasites. In the absence of feed intake, they can also experience sub-acute ruminal acidosis (SARA), leading to rumen microbe die-off and reduced nutrient absorption, opening them up to infection.

Types of lice found in cattle

There are two different groups of lice that the different species are divided into: sucking lice and chewing lice. Sucking lice feed on body fluids and skin secretions produced by the host, while chewing lice consume hair, skin and debris found on the body of their hosts.

Some of the most common species of louse found on cattle include the short-nose cattle louse (Haematopinus eurysternus), the biting or chewing louse (Bovicola bovis), the little blue cattle louse (Solenopotes capillatus) and the short-nose cattle louse (Haematopinus eurysternus). The variety of species can vary somewhat depending on region.

Heading off a serious infestation

One of the biggest mistakes made by producers is treating for lice too soon. Oftentimes, calves that are being weaned in the late summer and fall, prior to being moved to feedlots or pasture will be treated with either a pour-on dewormer or injectable dewormer. While this may have a small impact on the lice that are semi-dormant, it will not easily reach them if they have not moved to the upper portions of the animal. This means treatment is wasted and won’t prevent infestations from developing once the weather has truly gotten cold.

Pour-ons have shown the greatest efficacy, but the timing must be right. Early winter is an ideal time to treat for lice. It’s important to communicate with your herd veterinarian, as they will be able to advise on the most effective and economical timing.

How to help cattle that have already been affected

Even with good management, the weather can sometimes be a bit tricky and a serious infestation will occur. These animals will need a little extra help to regain their health and be able to withstand winter conditions. Here are a few things you can do to help your animals if they’re in this situation:

  • First and foremost, under the care of your herd vet, treat your cattle with a good pour-on dewormer formulated to kill the specific types of lice you are dealing with. Eliminating the cause of the irritation will help eliminate stress and allow any wounds to heal.
  • Treat ALL animals – even those that appear to be unaffected.
  • Base dosing on the weight of the animal. Too little and the product won’t work properly; too much is like pouring money down the drain.
  • Ensure complete coverage. The deworming product must come in contact with the lice themselves (or the areas they may migrate to) in order to be effective.
  • Help them reestablish normal eating patterns. This may require that problems like SARA are addressed. Neutralizing the rumen’s pH will encourage them to resume eating.
  • Support gut microbes. The rumen is responsible for 80% of the immune system’s ability to function. A very large part of this depends on a healthy microbial population. If the microbe balance has been disrupted, it will be necessary to provide nutritional support that will feed not only the animal but its damaged microbial colonies.
  • Take measures to help prevent recurrences, such as retreating at appropriate intervals during the winter months.

The time, money, and effort spent to properly treat your animals at the right times is a wise investment for the overall well-being of your herd. It will not only save them the discomfort of a lice infestation but can help boost your bottom line in the long run by preventing unnecessary shrink and illness.

© 2019 Pro Earth Animal Health.

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