LEECH HUNTING IN EAST AFRICA 
The leeches of Africa are less well known than any of the great continents . 
Thus wrote J. Percy Moore, the grand master of leech taxonomy, in his book 
African Leeches, published in 1939. His statement is just as true today, 
and was one of the spurs which urged me to Kenya in the summer of 1984, to 
f appalling gaps in the knowledge of Kenyan Hirudinea, 
I had worked previously on chenoreceptor systems in leeches, and was well 
acquainted with collecting and preservation techniques. T arrived in Kenya 
in early August with a collecting brief from the British Museum (Natural 
History), the blessing of the National Museums of Kenya and high hopes. 
Much of my work was based at Tony Dyer’s farm north of Timau, near Nanyuki. 
Collecting conditions could hardly have been worse. Kenya was crippled with 
drought in August and September, and the northern districts were particularly 
badly affected. No water means no leeches, many hours were spent mournfully 
dried river valleys, collecting jars optimistically at hand. 
The drought had another consequence; Boran, Somali and Samburu tribesmen 
h^ moved south in a desperate search for grazing. There were violent 
clashes on the Timau farms, and many potential collecting areas of northern 
Kenya were rendered effectively out-of-bounds. Nowhere in the Nanyuki area 
were leeches as numerous aa. I had expected. I spent many^ hours wading in 
rivers i^rticularly the Ngare Ndare and Naro Mom rivers) and paddling in 
swamps (including the apparently leech notorious Boranea swamps north-east of 
T^u) but remained unhappily unpunctured. Patiently I worked through all 
the techniques in the leech-hunters armoury. I exposed tempting ankles, and 
turned over stones. I paid African children to swim in deep pools and 
agitat^ the water with a white glove, which leeches often find irresistable, 
angled bleeding flesh baits into the water, and examined the mouths and 
nostri s of cattle as they returned from drinking. A few species were taken, 
but. in disappointingly small numbers. Cattle mouth and nostril leeches have, 
in the past, been a serious problem in the Nanyuki area. The dearth of 
leeches may perhaps be a result of reaction by the diligent farmers of the 
several cases where Copper Sulphate had been sprayed onto 
leech-infested areas. This will certainly eliminate the leeches, it may also 
be responsible for the general poverty of freshwater fauna which I saw. 
I had heard many attractive horror stories about the man-loving leeches of 
Lake Naivasha, and it was here that I searched next. I searched around the 
papyrus beds, and in the filters of the water pumps (often a fruitful source) 
b^ found none. The local Tilapia fishermen confirmed that leeches had 
eed been abundant in the lake until about seven years ago. Since that 
time leeches had never been seen. From several sources I pieced together the 
multi-stranded ecological background to this disappearance. 
A major factor was the appearance in the lake of Salvinla molesta, a free- 
tloating, non-flowering aquatic fern from South America. It is very fast 
growing and competes with native aquatic vegetation for light and nutrients. 
In Lake Naivasha the escalation of Salvinia heralded the end of the huge lily- 
beds which once bordered the lake. These lily-beds were the stronghold of the 
large leech population, and as the lilies disappeared, so did the leeches. 
With regard to leeches, the situation was compounded by the ill-advised 
application of a herbicide, Gramnoxone, in an attempt to control the Salvinia. 
5-6 litres of Grammoxona per hectare was sprayed onto Lake Naivasha, a 
concentration which would cause death to leeches and many other freshwater 
invertebrates* The details of the Saivlnia saga, and the ecological conseq* 
ucnces of the application of Graramoxone are documented in Stephen Njuna's 
article. ^ 
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