24 Feb 2022

Beef cattle rearing has been the backbone of Botswana’s economy since time immemorial.
However, cattle husbandry  is marred by numerous challenges such as theft and to a large extent, external parasites, which live and feed on the animal flesh, says Department of Veterinary Services surgeon, Dr Obakeng Kemolatlhe.
Dr Kemolatlhe, an  epidemiologist, says ectoparasites slow weight gain, lower milk production, degrade hide value, and have the potential to transmit diseases, thereby directly affecting the producer’s bottom line.
As such, lack of external parasite control costs beef producers millions of pula.
Dr Kemolatlhe says external parasites live on the surface of the host (animal)’s body on temporary or permanent basis, causing injury and in some cases, death.
The external parasites usually multiply rapidly as survival mechanism under natural environment.
Dr Kemolatlhe has decried that intensive farming or modern husbandry exacerbates parasite infestation as animals are kept close together in kraals or holding pens.
“The eradication is not always feasible as there might be different hosts involved in developmental stages of the parasite.
Adult parasites such as ticks are abundant in summer (rainy season) and easy to see with a naked eye from a distance, but not necessarily so for immature tick stages,” he said.
Dr Kemolatlhe said some external parasites infest wild animals as well, which then act as reservoirs and it is impractical to treat wild animals of external parasites, whose control involves prudent use of acaricides or dips or insecticides and vaccines; habitat manipulation and correct identification of such pests.
He said effects of ticks on the hosts include blood loss, direct damage to skin when attaching may cause inflammation and permit other pathogens such as maggots or screw worms, bacteria and viruses to enter.
Some ticks release toxins into the host through saliva when they suck blood.
He said the toxins can result in local reaction that may lead to skin discoloration, swelling or open wounds.
The ticks also transmit other disease-causing pathogens resulting infection with the likes of heartwater or anaplasmosis diseases.
Dr Kemolatlhe says although ticks feed on blood of host species, they are also well adapted to spending most of their time off the host in cracks, crevices and vegetation.
The preferred sites for ticks on hosts are ears, limbs, chest, abdomen, neck, udder and scrotum.
For tick control, the epidemiologist says there are various acaricides available in the market in the form of spot-on, sprays and pour-on formulations.
The spray formulations are those that are used in spray races or applied using container sprayers like knapsack sprayers.
He says these formulations involve dissolving the acaricides in water before spraying on to animals.
It is crucial to ensure that the spray acaricides reach the tick preferred sites of attachment.
The other formulation of acaricides is the pour-on formulations that are typically applied on the animals’ top body parts, usually from withers/shoulders to the tip of the tail.
These are generally oil-based formulations that are absorbed through the skin and ticks ingest them when sucking blood.
The spot-on acaricides are those that are applied directly to the ticks that are attached to the animal.
Dr Kemolatlhe advised farmers to adhere to withdrawal periods in relation to milk and meat consumption post treatment.
It is also critical to observe manufacturer’s instructions with regards to safe handling and application of acaricides as some can cause debilitating side effects or even death if overdosed.
Humans can also be exposed to acaricide poisoning through inhalation, swallowing or skin contact, therefore, handlers should be well informed and capacitated to handle such chemicals.
Acaricide poisoning in humans can have acute short term effects or long term effects that can occur after months or years post exposure.
Dr Kemolatlhe said some of the observed side effects include lacrimation/tearing with stinging eyes, blindness, rash, blisters, coughing, headaches, cardiac arrhythmias, nausea, vomiting, diarrhoea, abdominal distension, breathing difficulties, dizziness, convulsions, coma and even death.
The side effects mentioned are not exhaustive and they are also dependent on the exposure dose and the type of acaricide involved.
“There should be prudent use of acaricides as indiscriminate acaricides use may result in animals losing their acquired immunity to tick-borne diseases such as heartwater.
The strategy applied for tick control should maintain enough ticks on animals or environment to regularly re-infest and boost animal immunity, but not so many that they make animals suffer from direct ill-effects or compromised welfare state,” he said
He encouraged farmers to work closely with the veterinary extension officers, private veterinary surgeons and government employed veterinary surgeons in order to assist them to develop and implement an effective tick control strategy.ENDS