A research project was carried out between
October 1983 and June 1987 partly in Scotland and partly in
Cameroon covering three main areas: a survey on small ruminant
production and epidemiological and experimental studies on parasitic
gastroenteritis in these animals.
The survey on traditional management of sheep and goats
was conducted in North West Province of Cameroon using a
questionnaire. The main objectives were to assess the productivity,
to identify production constraints and to propose possible solutions.
Sixty-five farmers in Mezam division and 50 in Momo division were
interviewed. The results showed that 92% of the farmers rear goats
as against only 21% who rear sheep. A traditional belief by which
sheep keeping adversely affects a woman's fertility is perhaps the
greatest constraint on sheep production. Flock sizes are small,
typically 6-7 animals in single species flocks and up to 12 animals in
mixed flocks. Females make up 88% and 84% of sheep and goat flocks
respectively with 62% and 58% of the total sheep and goat flocks being
breeding females over 12 months of age.
Six management systems were identified. Those involving
tethering during the cropping season and either tethering or
semi-extensive grazing in the non-cropping season are most widely
practised. The most common housing system is an enclosed shed
with walls of sticks, tree fern or bamboo. Floors of planks laid on
the earth or slightly raised are used by about 48% of the farmers while
only 22% construct raised slatted floors.
Intentional feed supplementation is rare but salt is given by
most farmers on a more or less regular basis. Watering was not
considered essential by about 4% of the farmers.
Breeding is generally uncontrolled and progeny of the most
active breeding ram/buck is often the main source of ram/buck
replacement; therefore inbreeding is common.
Offtake rates were 20% and 24% in sheep and goats with flock
mean percentages of 26% and 23% respectively. The highest offtake
rates were recorded under tethering/semi-extensive (35%, and 28% for
sheep and goats respectively) and extensive/extensive (48% for sheep).
Mortality rates were not significantly different in either young
animals (17% and l4% in lambs and kids respectively) or adults (17% and
11% in adult sheep and goats respectively). There was some
suggestion of higher mortality rates under
semi-intensive/semi-intensive and semi-intensive/semi-extensive
management systems. Tick infestation and diarrhoea were
considered to be among the major causes of death. Five disease
problems of small ruminants were identified on the basis of the
signs reported by the farmers: intestinal parasitism especially
helminthiasis, tick infestation and the viral diseases associated with
it, pneumonia, peste des petits ruminants and Oestrus ovis
infestation. Traditional medicine for treatment of sick animals is
practised on a very small scale with very limited success.
sed on a very small scale with very limited success.
A survey on haemoglobin types was carried out on sheep and
goats collected from the North West Province and Northern
Cameroon as background studies to the experimental work on
haemonchosis. Three adult haemoglobin variants (HbA, HbB and
HbC) were identified. Haemoglobin types A and B occurred in sheep
and haemoglobin types B and C in goats. The gene frequencies of
the A and B alleles were 0.08 and 1.00 in Grassland Dwarf sheep and
0.06 and 1.00 in Fulani Bornu sheep. In the goats the gene
frequencies of the B and C alleles were 1.00 and 0.15 in Grassland
Dwarf goats and 1.00 and 0.38 in Red Sokoto goats. Abnormal
production of a haemoglobin with similar electrophoretic mobility to
Hb type C was observed in both species under haematological
stress. The intense selection of the B gene in the sheep and goat
population is of potential interest.
The epidemiological studies were intended both to examine
the factors which predispose sheep and goats to helminth infections
and their effects on production, and to evaluate the efficiency of
various control measures intended to increase production. The
regime of monthly deworming with fenbendazole currently practised
at the research station was used as the control for the first year's
epidemiological study designed to investigate the effect of reducing
the frequency of such treatment on the survival and productivity of
small ruminants. Three management systems were compared: the
control regime, a regime involving five strategic treatments and
traditional village management with no anthelmintic. The
performance of the animals was monitored for one year. At Mankon
the goats gained less weight than the sheep. On the contrary the
traditionally managed goats both survived better and gained more
weight than traditionally managed sheep
The strongyle faecal egg counts from both sheep and goats
fell at the start of the dry season and remained low until April
regardless of the system of management or the frequency of
anthelmintic treatment. Pasture larval counts and infection levels in
tracer animals were low during this period. During the rainy season
faecal egg counts were consistently lower in sheep at Mankon than
in goats while in the village animals the reverse was the case. In
the animals at Mankon, egg counts made 15 days after treatment
were similar to the pretreatment counts. The possibility of
benzimidazole resistance by the trichostrongyles in the animals at
Mankon was suspected and confirmed by conducting egg counts one
week after treatment and by an in vitro anthelmintic sensitivity test
in which it was shown that strongyle eggs from the animals at
Mankon consistently developed in higher concentrations of
tiabendazole than eggs obtained from the village animals.
Pasture larval counts were high during the rainy season
producing two waves of larval contamination on the pastures, one in
mid-June and the other towards the end of the rains in November.
The period of maximum infection in tracer animals followed the June
peak of pasture contamination. High mortality in traditionally
managed sheep in July, August and September also coincided with
periods of heavy larval challenge. Haemonchus contortus,
Trichostrongy/us axei, Trichostrongy/us coiubriformis and, to a lesser
extent, Moniezia expansa were prevalent throughout the year but
with larger numbers present during the rainy season.
Oesophagostomum columbianum and Bunostomum trigonocephaium
were prevalent mainly during the rainy season, heavy burdens in the
animals dying during the dry season apparently having been acquired
in the late rains
The primary haematological parameters (PCV, Hb
concentration and RBC counts) in the animals at Mankon tended to
be low during the dry season but increased at the onset of the rains
and changed very little thereafter. However, in the traditionally
managed sheep, the values of these parameters tended to decline
overall. In general the haematological values were somewhat lower
in the animals on the reduced regime than in those on the standard
regime, and in the traditionally managed sheep and goats than in
those at the research station.
In the animals at Mankon, the serum total protein and albumin
concentrations were low during the dry season. In sheep the total
protein increased significantly at the beginning of the rains while the
albumin changed very little throughout the year. In goats the
albumin concentration showed a more or less steady fall throughout
the study. In all animals the globulin values were generally elevated
during the rainy season. Serum pepsinogen levels were low during
the dry season but increased during the rainy season. In the
traditionally managed animals the serum biochemistry did not change
significantly throughout the study.
The second year of the epidemiological study examined the
possibility of further reducing the frequency of anthelmintic
treatment when an effective anthelmintic is used. The experimental
groups received either four or two strategically timed anthelmintic
doses, the traditionally managed group included an on-station
simulation study and a group of sheep and goats were kept together
on mixed grazing.
In this year the survival rate was significantly higher in sheep
than in goats under all management systems except in those on
The faecal egg count patterns in all the groups during the dry
season were similar to the previous year. Following anthelmintic
treatment in the 4-dose group with levamisole in early March, the
faecal egg counts were initially reduced to zero in both sheep and
goats. Under both the 4-dose and 2-dose regimes treatment with
levamisole maintained egg counts in all animals at less than 200 epg
throughout the rainy season. Nevertheless the goats at Mankon still
carried slightly higher egg counts than sheep. Traditionally managed
animals again showed higher egg counts in sheep than in goats.
Although the peak periods of pasture larval contamination
were modified by the anthelmintic treatments, the overall pattern of
seasonal availability of trichostrongyles remained unchanged.
Sheep maintained higher PCV values than goats throughout
the year. There was a similarity in the serum protein patterns in all
groups in both hosts with a tendency for the albumin levels to
remain fairly constant and for the globulin levels - and hence the
total protein - to fall or remain static during the dry season and then
to rise during the rainy season. No consistent differences were
found between age or treatment groups but some of the changes
with time were significant.
The albumin values determined by the bromocresol green
method were consistently and significantly lower in goats and higher
in sheep than those determined by electrophoresis.
The experimental studies largely reflected and amplified the
epidemiological findings. The development of the parasite and its
relationship to haematologicai, biochemical and pathological changes
were studied in lambs and kids after a single infection of 10,000 L3
of Haemonchus contortus In Scotland using a local sheep-adapted
strain (ES) and European lambs and kids, the PCV and Hb
concentration in the lambs declined rapidly from day 10 after
infection whereas in kids this was less marked and there was an
initial rise in these values during the first three days following
infection. Localized areas of mucosal hypertrophy were visible on
the abomasal surface by day 4 and a coagulum covered the fundic
abomasal surface on day 8 in both lambs and kids and on day 14 in
the kids only. There was a steady reduction in the number of worms
recovered with age of the infection, more dramatic in kids than in
lambs. The infections were accompanied by mucosal hypertrophy
and infiltration of lymphoid-type cells, plasma cells and eosinophils.
Desquamation of the mucosal epithelium was visible from day 8.
The single infection studies at Mankon compared the
response of indigenous lambs and kids to infection with three strains
of Haemonchus contortus, two derived from local goats (LG) and
sheep (LS) respectively and one ES strain. The primary
haematologicai parameters were more severely lowered in kids than
in lambs for at least 12 days after infection. The depression was
more severe in animals infected with the LS strain than in those
infected with the LG or ES strains. The changes in serum protein
biochemistry were less marked but with an overall tendency for the
total protein and albumin to fall after day 12 in animals infected with
the LG and LS strains. Female worms in both hosts were clearly
larger than the male worms from day 8 and the worms from the
lambs were clearly much bigger than those from the kids from day
11. Sexual maturation was reached earlier in the worms from the
lambs than in those from the kids. The pathological changes were
similar to those seen in the infections in Scotland. However, the
coagulum was observed in kids infected with the LG and LS strains
killed on days 8, 11 and 14 whereas in lambs it was observed only in
those killed on day 11. No signs of gastric haemorrhage were
observed in any of the indigenous animals infected with the ES
strain. Overall the severity of the parasitic effects was greater in
kids than in lambs and in animals infected with the two local strains
than in those infected with the ES strain.
The epidemiological pattern observed in temperate countries
at the end of the winter was simulated by an escalating infection
study. European lambs and kids were infected with increasing doses
of H. contortus (ES strain) twice weekly for five weeks. Results
showed depressed liveweights in lambs from six weeks onwards.
Anaemia developed in the course of the infection, being more severe
in the lambs than in the kids. Serum total protein and albumin
dropped significantly in the lambs while the changes in kids were not
significant. Serum pepsinogen concentration rose during the
infections, the rise being more consistent in the kids. Lambs had
significantly more worms, a shorter prepatent period and higher
faecal egg counts than kids.
The daily infection of indigenous lambs and kids in Cameroon
with small doses of the two local strains of Haemonchus contortus
was intended to simulate a field situation in which animals are
grazing continuously on lightly contaminated pastures. The results
showed that there was considerable reduction in liveweight of the
kids compared to the controls whereas the growth of the lambs was
not affected. Most of the higher faecal egg counts in kids were in
animals infected with the LG strain whereas in lambs it was the LS
strain that gave rise to the highest counts. However, throughout the
20 weeks of the study most animals had less than 500 epg in their
faeces. Necropsy worm counts revealed that kids carried higher
burdens of the LG strain and lower burdens of the LS strain than
lambs, but the counts in all cases were generally less than 600 per
animal. There was a prolonged depression of the primary
haematological values in kids infected with both strains of H.
contortus whereas these values in lambs fluctuated within the
pre-infection range. Serum protein biochemistry did not change
significantly while serum pepsinogen levels increased in the course
of the infection.
It was concluded that a management regime utilizing three
strategic anthelmintic treatments under set-stocking conditions is
indicated for controlling parasitic gastroenteritis in sheep and goats
kept on the research station in the North West Provice of Cameroon.
In the villages treatment, especially of sheep, during the rains may
be beneficial and cost-effective.