Tsetse - the silent destroyer

If you haven't read my previous post (July 17) then stop and go back.  

When I became a "tsetse fly controller," or Glossinologist, in 1967 I had only a rudimentary understanding of the insect and little appreciation of the total control this fly had on huge areas of the African continent.  In Rhodesia, as in so many developing countries, there was an unrelenting need for more land where the rapidly growing rural population could establish their rudimentary houses, grow crops and raise livestock. 

Wherever the tsetse fly occurred, rearing cattle, both as a source of meat and milk and as draft animals, was not possible without expensive prophylactic drugs administered every 30 days.  Almost 25% of otherwise fertile land in the country could only be farmed with hand tools, making it subsistence living or worse. The government had, over the years after WWII, put ever-increasing financial and manpower resources into finding ways of pushing the tsetse fly away from suitable areas planned for settlement.  Most of these efforts were restricted to the dry months of the year, generally from May through September; or, if the rains came late, the month of October could be included in that calendar.  The rains, from October through April, and sometimes May, were a huge impediment to field operations against the tsetse fly in Rhodesia.

The unique biology and behavior of the tsetse fly made it vulnerable to two primary control methods.

First:  it is very susceptible to insecticide.  It also tends to rest on the bark of trees along drainage areas which provide it with shade and sandy soil where it lays its already developing pupa.  These areas are where water sources for wildlife can be found and where wildlife tends to find shelter in the heat of the day.  The careful, targeted, application of insecticide to specific tree species could significantly reduce the populations of the fly.  It was possible to pinpoint these drainage areas by using aerial photographs. The targeted applications of insecticide also mitigated to a large degree the dangers of the widespread use of toxic chemicals on many other species of birds, insects and mammals.

Application of insecticide in a remote area in north Rhodesia.

In the 1960s there was a great sensitivity to the dangers of indiscriminate insecticide applications.  DDT had been banned in many parts of the world and it was in short supply locally.  We had turned to using Dieldrin which was more toxic than DDT but which could be applied in lower concentrations to achieve a similar result in reducing fly populations.

Second:  its preferred food source is the blood of mammals occurring in the wild.  In Rhodesia in the 1960's, the list of the top six preferred animals was made up of elephant, cape buffalo, warthog, bushpig, kudu and bushbuck.  All of these species were carriers of the disease passed on by the fly (trypanosomiasis or "tryps") but were resistant to its effects.  By establishing "controlled hunting areas," populations of these animal species could be selectively reduced or driven out by hunting.  Once these populations were reduced sufficiently the fly could not sustain itself in the area and would die out.  Depending on the success of controlled hunting in one area, resulting in the removal of the fly, the boundary of the controlled hunting areas could be moved each year, thus opening up new land for farming.

Another important consideration was that the tsetse fly could not fly long distances and would not, on its own, move across areas which were dry and did not have suitable shelter.  So their movement was greatly aided by the presence of animals which moved long distances - especially elephant and buffalo.  Tsetse fly were thought to be moved by resting on the skin of elephants as they traversed great distances to find water.  To inhibit the movement of these animals 7 ft. high game fences were erected across great distances, at considerable expense.

The two control methods discussed here, when coordinated with one another, would result in the removal of the fly from widespread areas of the country.  But how did we measure the success of these methods?  Checkpoints (or "fly gates") were set up at strategic points along the areas under attack.  The Tsetse Fly, attracted by dark colors and moving objects, would often rest in the wheel wells of cars.  A gate attendant at a "check point" would walk around the vehicle with a small net in hand and attempt to capture any flies.  These would be counted and recorded.  Over time, his daily log would be handed in and the figures added to maps back at Tsetse Control Headquarters.  These somewhat crude methods gave a good indication of the presence of the tsetse in those sensitive front line areas and helped to plan future campaigns.

A typical rural Tsetse Fly gate in 1960s Rhodesia.

Anyone who may have lived or traveled in Rhodesia (Zimbabwe) in the 1960s and 1970s will remember the Tsetse Control Check Point on the highway north leading to Zambia and Lake Kariba.  Every southbound vehicle had to pass through a large hangar expressly constructed for the purpose of capturing flies and monitoring fly numbers. (Unlike the photo shown here, which is a typical small fly gate in a remote area.)  When all the cars and trucks that could fit were inside, the large hangar doors at each end were closed, making the inside dark.  A hand held aerosol insect repellent was spayed into the car or cab of the truck and into the wheel wells of the vehicles.  Small windows were opened in the hangar wall to let in light through a trap.  Attendants would wave their nets around the wheels to stir the flies up.  Flies would either be caught in the nets or attracted to the light boxes in the hangar wall.  This hangar provided  valuable fly counts each month which gave excellent statistics to determine fly populations.

I could write at great length about the massive efforts to push the tsetse away from areas of settlement in Rhodesia.  These efforts continue today in many countries of Africa.  I personally would not trade my time in this effort for anything.  One benefit was that I was always working in areas with very high wildlife populations.  Over one seven-month period from April to October 1968 I lived on the southeast border of Rhodesia, working on a three-country control operation along the shared border with Mozambique.  Teams from South Africa, Mozambique and Rhodesia worked together on this huge effort which consisted of opening up an expensive new road system in the Portuguese territory.  This area of southeast Rhodesia would in later years become the Gona-re-Zhou National Park and may soon be extended across Mozambique into the Kruger National park of South Africa to create a massive "Trans-Frontier Park." The Gona-re-Zhou ("place of the elephants") is one of the most stunningly beautiful areas of Africa. When I was camping there I saw huge herds of cape buffalo and elephant. Two large perennial rivers, the Save and the Lundi Rivers flow through here which support rich game populations in the surrounding hills and plains.

On maps of this area today you can see a small dot along the border labeled "Border B" representing a gate in the fence line.  While I was planning the new road system (using aerial photographs) I selected that point along the fence for construction of a gate between the two countries. Because it occurred at point "B" on an expansive A, B, C, D grid system, I named it Border B Camp.  That name has stuck.  Maybe I should have called it Joe's Gate, or something more descriptive.

If I could have an opportunity to re- visit one part of Africa before I cash in my chips, I would like it to be the Gona-re-Zhou National Park. 

Next: Some animal encounters.