Ticks are the most important ecto-parasites of livestock in tropical and sub-tropical areas. They are responsible for severe economic losses both through the direct effects of blood sucking and indirectly as vectors of pathogens and toxins. Feeding by large numbers of ticks causes reduction in live weight gain and anemia among domestic animals while tick bites also reduce the quality of hides. However the major losses caused by ticks are due to the ability to transmit protozoan, rickettsia and viral diseases of livestock, which are of great economic importance world-wide.
There are at least 840 tick species in two major families, namely the Ixodidae or ‘hard’ ticks (so called by virtue of their hard dorsal shield) and the Argasidae or ‘soft’ ticks (due to their flexible leathery cuticle). The family Ixodidae comprises approximately 80% of ail tick species, including the species of greatest economies importance.
Types of ticks
American Dog Tick (Dermacentor variabilis): One of the most frequently encountered ticks is the American dog tick, also sometimes known as the wood tick. The larvae and nymphs feed on small warm blooded animals such as mice and birds. The adult American dog tick will feed on humans and medium to large mammals such as raccoons and dogs. Unfed males and females are reddish-brown and about 0.19cm long. Females have a large silver-colored spot behind the head and after feeding will become 1.27cm long about the size of a small grape. Males have fine silver lines on the back and do not get much larger after feeding. Males are sometimes mistaken for other species of ticks because they appear so different from the female. The American dog tick can transmit Rocky Mountain spotted fever, tularemia, and possibly ehrlichiosis to humans.
Lone Star Tick (Amblyomma americanum): Larvae, nymphs, and adults will feed on a variety of warm blooded hosts including people. The larva is very tiny only a little larger than the period at the end of this sentence. The nymph, the most common stage found on people, is about pinhead-sized. Adults are about 0.32cm long and brown. The adult female has a white spot in the middle of her back. The lone star tick is most active from April through the end of July. Although it can transmit Rocky Mountain spotted fever, the lone star tick is not as likely to transmit the disease as the American dog tick. This tick also may transmit tularemia and ehrlichiosis to humans. The lone star tick is not believed to transmit the bacteria that causes Lyme disease (Borrelia burgdorferi), but it may be associated with a related bacteria species that has not been completely identified.
Blacklegged Tick, also known as the Deer Tick (Ixodes scapularis): All three active stages of the blacklegged/deer tick feed on a variety of hosts including people. After the eggs hatch in the spring, the very tiny larvae feed primarily on white-footed mice or other small mammals. The following spring the larvae molt into pinhead-sized, brown nymphs that feed on mice, larger warm-blooded animals, and people. In the winter they molt into adults that feed primarily on deer, with the females laying eggs the following spring. Adults are reddish-brown and about 0.32cm long (or about one-half the size of the more familiar female American dog tick). These ticks are found in wooded areas along trails. The larvae and nymphs are active in the spring and early summer; adults may be active in both the spring and fall. The blacklegged/deer tick can transmit Lyme disease and possibly ehrlichiosis to humans.
Brown Dog Tick (Rhipicephalus sanguineus): The brown dog tick (also known as the kennel tick) is found through most parts of the world. This tick feeds on dogs, but rarely bites people. Unlike the other species of ticks, its life cycle allows it to survive and develop indoors. The brown dog tick is found primarily in kennels or homes with dogs where it may be found hiding in cracks, behind radiators, under mats and furniture, and on draperies and walls. The adult is reddish-brown and about 0.32cm long and usually attaches around the ears or between the toes of a dog to feed. After feeding, a female may engorge to 1.27cm long. She then drops off the dog and crawls into a hiding place where she may lay as many as 3,000 eggs. The brown dog tick is not an important carrier of human disease.
Winter Tick (Dermacentor albipictus): The winter tick is a species that feeds on large mammals like deer, cattle, and horses. Unlike the hard ticks mentioned above, the winter tick attaches to the host as a larva and remains attached throughout its life. Consequently this tick is rarely encountered by campers or hikers. Hunters may however find the winter tick in large numbers on deer carcasses. Although the winter tick may carry diseases of large wild mammals, it is not known to transmit disease to humans.
Methods of controlling ticks
There are different methods of tick control. The one that will work best for the community will depend on many factors such as the number of cattle, the facilities available, the tick and tick-borne disease situation in the area, how you want to control ticks (for example, whether you want to use strategic or intensive control) and the amount of money available for dipping compounds.
- The plunge dip is one of the common methods of tick control. The animal is completely immersed in the dipping compound. You need a dip tank, an electric or diesel pump and access to water.
- Spray races are sometimes used. The animal walks through a race where it is sprayed with the dipping compound. You need a spray race, an electric or diesel pump and access to water.
- Hand spraying can be used. The dipping compound is applied to each animal with a hand-operated spray. This can be time consuming. You need a back-pack spray.
- Hand dressing or spot treatment involves treating the sites where ticks commonly occur. Tick grease, oil or dipping compound can be used.
- Pour-ons are dipping compounds which are applied on the back. They are easy to use, but can be expensive compared to other options.
- Injectable compounds are effective for some ticks, such as blue ticks, but not for all. They work through the blood.
- Other methods such as removing ticks by hand, the use of chickens to remove ticks and pasture management, can also be considered.
- Movement of animals can spread ticks to other areas. It is recommended to treat cattle before moving them or introducing them to your herd.
- Whichever method to be applied, always follow the directions and mix the dipping compound appropriately.
- Home-made remedies can be ineffective, lead to resistance problems and can be very poisonous and cause skin damage to the animals. Never use home-made remedies!