Staff Reporter
Windhoek-Rains over most parts of the country lately have brought along the dreaded ticks and tick-borne diseases in cattle.
Farmers in all cattle-rich areas are reporting the presence of extremely high populations of the most commonly found ticks in Namibia. Ticks and tick-borne diseases affect livestock, human beings and domestic pets. In particular, cattle ticks can inflict severe economic losses, with costs associated with parasite control along with losses in fertility, body weight and milk production. Veterinarians are thus urging all livestock producers to take the necessary precautions and dip their animals regularly. The cattle tick (Rhipicephalus microplus) adapts quickly to areas where it has been ‘introduced’. Larvae gather on the soft skin of an animal, such as the inner thighs, flanks, forelegs and abdomen. Its habitation is the savannah wooded grasslands with cattle its primary hosts though it will also utilise horses, donkeys, sheep, pigs and occasionally sheep and buffalo.
Tick-borne diseases include the Asiatic redwater, bovine babesiosis and anaplasmosis (caused by Anaplasma marginale) or gallsickness. The animal shows reduced weight, and decreased milk yield. R. microplus can build up acaricide resistance more rapidly than most other tick species, so avoid prolonged treatment with a single acaricide. If there is resistance to both organophosphate and chlorinated hydrocarbon acaricides, carbamate acaricide can be effective. Another option is regular dipping until the livestock are tick-free. After two more dips, send the animals to a tick-free pasture. The pasture they were removed from must lie idle for six to 10 months. The novel cattle tick vaccine can be used as an alternative to dipping.
Amblyomma hebraeum (Bont tick)
A male bont tick. Males reach a length of 6mm, while females can be 5mm long. Both sexes have large, powerful mouthparts capable of causing considerable damage to the host.
Bont (Afrikaans for ‘colourful’) ticks are typically found in short pasture. They collect on the lower legs of animals, or between their hooves, and crawl from there to their chosen feeding site, usually around the hairless regions of the body such as the genitalia and underbelly. They thrive in the egret distributing it widely on the continent. It has been recorded in at least 30 countries, including Namibia. They are parasites of cattle, goats, sheep, horses and dogs, as well as antelope and birds.
One of the main diseases spread by the tick is heartwater (Ehrlichia ruminantium), where fluid develops around the heart and lungs. Mortalities can be as high as 80% in infected animals. An additional problem is potential blood loss. Before dropping off to lay its eggs, a female tick can consume up to 20ml of blood. A heavy infestation can lead to weight loss, reduced appetite and a predisposition to other diseases. Signs include nervousness (more obvious in cattle than sheep or goats), difficulty in walking, respiratory distress, convulsions and death.
Control can include movement restrictions, pre-export inspection, quarantine and treatment with acaricides while the tick is on the host animal. It has been suggested that livestock should not be reintroduced into pasture where measures have been in place to eradicate the tick for at least four years. A heartwater vaccine is available, and animals respond well to treatment with
tetracycline.