The State Veterinary Services completed their annual tsetse fly surveillance in the Kruger National Park in the last week of April. According to Dr Roy Bengis, this is the twelfth year in a row that the surveillance has taken place. To date, no tsetse flies have been detected in Kruger. Tsetse flies transmit the parasite that causes nagana (sleeping sickness, trypanosomiasis), in much the same way as anopheles mosquitoes transmit malaria.
Dr Bengis says that although the disease has not been present in Kruger for over a hundred years, it is only a watershed away, as it occurs in Gonarezhou National Park in Zimbabwe. Prior to the massive rinderpest outbreak in southern Africa at the turn of the last century, the disease was prevalent in Kruger. Dr Bengis says that the disease is not a concern to wildlife, as they have a long evolutionary history with the parasites.
However, trypanosomiasis is fatal to cattle, horses and dogs, and can infect humans. If the fly were detected in Kruger, the cattle on the park's boundaries would have to be protected by means of tsetse fly control programmes. Such programmes have been implemented in neighbouring countries. To inspect for tsetse flies, a cunning trap is used. Blue and black plastic sheeting of a specific colour is shaped into a tent-like structure, and in each trap a specially formulated liquid is placed.
This contains compounds that are found in the breath of herbivorous animals that bloodsucking flies like to bite. As the liquid evaporates, the flies follow the smell to the trap, where they land on the black plastic and are eventually led into a bottle. The contents of the bottle are examined using a magnifying lens on a daily basis. The traps are placed in a variety of habitats, such as along rivers, in mopani bushveld and in savanna areas. Dr Bengis remarked that this year significantly fewer flies were trapped than previously, something he attributes to the poor and patchy rainfall.