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Disease syndromes in sheep and goats naturally infected with Trypanosoma congolense
J. COMP.
PATH.
1979.
DISEASE
YOL.
457
89.
SYNDROMES NATURALLY
IN SHEEP INFECTED
TRY’PANOSOMA
AND WITH
GOATS
CONGOLENSE By
L.
and El
GRIFFIN* Veterinary
W.
Sercices DiziJion,
ALLONBY~ hhbete,
Kensa
INTRODUCTION
Until recently trypanosomiasis was not regarded as an important disease of* sheep and goats. Kramer (1966) reported that the disease in Nigeria was of little importance in these hosts, and Stephen (1970) and Finelle (1973) stated that sheep and goats are seldom infected with trypanosomiasis under natural conditions. However, more recent work indicates that not only are these animals naturally infected by this disease, but that high mortality can OCCUI (Mackenzie and Cruickshank, 1973; Griffin and Allonby, 1979a) and these animals may be important in the transmission of trypanosomiasis to other stock (Mahmoud and Eimalik, 1977). The pathology and pathogenesis of experimental trypanosomiasis in sheep and goats has been studied (Losos and Ikede, 1972; Ikede and Losos, 1975; Mackenzie and Cruickshank, 1973; Mackenzie, Boyte, Nesham and Piric, 1972)) but the various syndromes produced by natural infections have not been clearly described. During an epidemiological study of trypanosomiasis in sheep and goats grazed in an endemic area of Kenya it became apparent that not only are these animals severely affected by trypanosomiasis (Griffin and Allonby, 1979a) but that the disease caused by Tr@anosoma congolense, the only species detected, could be divided into three syndromes based on the duration of detectable parasitaemia. These syndromes produced by the naturally acquired infection are classified and described in this paper. MATERIALS
AND
METHODS
Two breeds of sheep and two breeds of goats, all adult castrates raised in tsetsefree areas were grazed in tsetse-infested rangeland at the Kiboko Range Research Station and the naturally acquired infection was observed for 8 months. Sixteen purebred Galla and 23 Saanen Y Galla crossbred, the first cross between indigenous Galla and the imported Saanen breed, were the goats used. Seventeen local Blackhead Persian and 12 imported Karakul animals were the two breeds of sheep studied. The study area, vegetation, climate, tsetse species and experimental breeds have been described previously (Griffin and Allonby, 1979a). * Present address: P.O. Box 30020, Nairobi, Kenya. t Present address: Animal Health Officer, U.N.D.P.,‘F..\.O. P.0. Box 30218, Nairobi, Kenya. 0021-9975/79/040457+08
$02.00/O
Sheep and Goat
~cs 1979 Xcadcmic
Development
Prejs Ix.
(London)
Project. Limited
458
L.
GRIFFIN
AND
E.
W.
ALLONBY
Packed cell volume (PCV) and rectal temperatures were recorded twice per week, and body weight was measured weekly. Diagnosis of trypanosomiasis was made on the basis of Giemsa stained thick blood smears. RESULTS
The species of trypanosomes detected were classified morphologically according to Hoare (1972). In all cases the species identified was irrypano~oma (Nannamonas) congolense, referred to as T. congolense. Among the breeds of indigenous and exotic sheep and goats naturally infected with T. congolense different patterns of disease emerged which can be divided into three main groups according to the duration of the infection. Within two of these groups another division can be made based on the outcome of the disease, either fatal or “self-cure”, but in the third division the outcome always proved fatal. (1) Acute This was defined as those infections which lasted up to 6 weeks from the first appearance of parasites in a thick blood smear. (a) Fatal. If the outcome was fatal, as exemplified by the clinical data of the case shown in Fig. 1, the disease was characterized by a rapid decrease in PCV to below 15 per cent in some cases. From the time that parasites were detected the body temperature fluctuated widely, at times reaching as high as 41 “C. Due to the rapidity with which death ensued there was very little loss in body weight and the general condition of the animal at death was usually good.
.
30 -
PCV
(%)
L>L-
-
35 30-
\
l -..
l we\
7,,.-/‘lo
25 20-
\ %
28 ;;$
weight 26
24 22 Period of detectable parasltaemia
0
I
I
I
I
I
2
4
6
8
IO
12
14
16
18
Time in weeks
Fig.
1. Clinical data of a goat with of detectable parasitaemia.
a naturally acquired trypanosome Type la Acute, fatal.
infection
in relation
to the period
TRYPANOSOMIASIS
IN
GOATS
AND
-1-59
SHEEP
(b) Self-cure. If not fatal the outcome of the disease was a self-cur? by t hc host after a brief appearance of the parasite in the peripheral blood (Fig. 2). In such cases the temperature was slightly elevated during the period of detectable parasitaemia but returned to normal quite rapidl) when parasites disappeared. The PCV decreased slightly, but rcturncd rapidly to normal, the weight remained steady and there ~vas littlc change in body condition. 40 Body temperature PC)
Rudy (kg)
.
3g
A.,/\
38-o-
/l,e
./‘.-fl
.
A
weight
2. CIinical period
l -.------•
//----.-.-/*’
0
i:ig.
. ,
.
2
4
6
data of a sheep with of detectable parasitaemia.
8
IO
a naturally Type
12 Time acquired 1b Acute.
14 16 in weeks
18
trypanosomr sell-curt.
20
22
inf‘cction
24
26
in rel;ttion
28
to the
12 ) ,Suh-acute This group includes those infections which terminated betwecll 6 and 12 M-eeksafter the initial appearance of parasites. (a) Fatal. In fatal cases the PCV usually showed a marked and stcadv decline early in the infection, as exemplified by the case shown in Fig. 3. and the PCV remained between 15 and 20 per cent for some weeks before death. The temperature showed wide fluctuations from the onsrt of disease between 38.3 “C to 40-O “C. but often remained high for some days immediately prior to death. The weight loss was usually marked at the beginning of the disease, but remained steady latterly, and the host became emaciated, lethargic and its condition poor. (C,; b5’e(f-cure.Those animals which effected a self-cure showed a rapid decrease in PCV with the onset of a detectable parasitaemia. However. the‘ PCV began to increase steadily during the later stages of the disease when the parasitaemia decreased, and reverted rapidly to normal with the disappearance of the parasites (Fig. 4). Thr temperature increased hricfly at the height of diseasebut this was short-lived and it soon dropped to normal. There was usually loss of appetite, and lethargy in the fatal cases, but in those animals which underwent self-cure, rven if the condition of the animal deteriorated initially, it improved with the disappcarancc of the parasites.
460
L.
GRIFFIN
AND
E.
W.
ALLONBY
46 Body (kg)
weight44
/* \
l C.b.
42 Period of detectable parasitaemia 0
2
4
mm 6 Time
Fig. 3. Clinical data of a goat with a naturally acquired of detectable parasitaemia. Type 2a Sub-acute,
Body weight
8 IO in weeks
12
trypanosome fatal.
14
infection
IC
in relation
to the period
35 25 -
Period of detectable parositaemia
e 0
2
4
6
Fig. 4. Clinical data of a goat with of detectable parasitaemia.
8
IO
12
14
I 16 18 20 22 Time in weeks
a naturally acquired Type 2b Sub-acute,
trypanosome self-cure.
1 24
1 26
infection
t 28
t 30
I 32
in relation
I 34
L 3l
to the period
(3) Chronic This category includes all those infections with a parasitaemia lasting over 12 weeks and is exemplified by the clinical data shown in Fig. 5. The parasites were detectable by thick film only intermittently, but nevertheless disappeared and reappeared over a long period. The temperature showed wide fluctuations between 37.7 “C and 40.5 “C and in some cases regular peaks at about 40.5 “C
TRYPANOSOMIASIS
IN
GOATS
AND
461
SHEEP
occurred every 5 or 6 weeks. The PCV showed an initial decline at the onset of infection but remained at 20 to 25 per cent with small fluctuations during the course of the disease, depending on the parasitaemia. The weights showed similar patterns with a decrease followed by a period of steady weight. In all cases the animal became emaciated, the coat dry and staring and the general condition poor, with death as the final outcome.
Body
Body weight (kg)
25 .~~-------*\
20
-/-0..
Fiz%[;io d 0
Fig.
J 2
4
6
8
IO
12
14
16 18 20 22 Time in weeks
5. C:linical data of a sheep with a naturally acquired period of detectable parasitaemia. Type 3 Chronic.
24
26
trypanosome
28
30
32
infection
34
36
in relation
to the.
The number of animals of each breed showing the various syndromes is shown in Table 1. The crossbred goats, the Saanen x Galla and the exotic Karakul sheep showed a higher percentage of deaths out of those becoming infected than the indigenous breeds, 77 and 71.4 per cent compared with 20 and 22 per cent respectively. This is reflected in the larger numbers of infected indigenous animals which effected a self-cure compared with the exotic and crossbred sheep and goats. TABLE
1
$,ndromes Total Breed
number
Saanen x Galla goat Galla goat Karakul sheep Blackhead Persian sheep * Deaths
23 I; 17
JVumber infected
Deaths h’umber (Per cent)*
9 5 7
7 1 5
(20)
9
2
are a percentage
(77)
1. .lcute Fatal
Self-cure
2. Sub-acute Fatal Self-cute
1 2 2
3 0 2
i
(714)
2 0 0
(22.2)
2
3
0
‘l
of the numbers
of infected
animals
in the group.
1
3. C’h~onA
I,
i 3 0
462
L.
GRIFFIN
AND
W.
E.
ALLONBY
DISCUSSION
The disease syndromes in sheep and goats described here conform closely to those described by Mackenzie and Cruickshank (1973) in nine naturally infected Blackhead Persian sheep. They divided the animals into three groups according to the disease pattern observed. Three animals showed an acute infection lasting up to 43 days before death, characterized by a rapid fall in red cell indices, as occurred in Group 1 (a). Animals of their second group showed a chronic infection of 11 and 12 months but terminated by an acute phase immediately before death. This acute phase was not observed in any of the sheep or goats with the chronic or sub-acute infection from Kiboko. However, the sheep described by Mackenzie and Cruickshank (1973) proved to have a mixed infection of T. congolense and T. z&ax, and the latter may have been responsible for the acute phase just before death. These authors also described a third group which showed a protracted course of infection of unspecified duration, but with no acute phase prior to death, and corresponding with Group 3 described in the present study. The apparent self-cure was not described by Mackenzie and Cruickshank (1973) possibly because fewer animals or more virulent strains of parasite were used. Losos (personal communication) described three patterns of disease in cattle experimentally infected with T. congolense, namely acute, chronic and asymptomatic. Cattle in the third group supported a parasitaemia which was high at times, but without showing clinical signs. This was not observed among the naturally infected sheep and goats. If a parasitaemia was detected a reduction in PCV and fluctuation in temperature were also observed. Dargie, Murray, Murray, Grimshaw and McIntyre (1979) demonstrated that in two breeds of cattle, the N’dama and the Zebu experimentally infected with T. congolense, the severity of the disease as monitored by the anaemia was correlated with the height and duration of parasitaemia. Although parasitaemia height could not be determined in this study the presence of parasites in the peripheral circulation was reflected in the change in PCV. However, Dargie et al. (1979) also noted that PCV values showed little tendency to recover even with the disappearance of parasites from the blood. In this study, by contrast, the PCV invariably returned to normal shortly after the disappearance of parasites. This may also be linked to the fact that in these cases the temperature which fluctuated widely during parasitaemic periods also returned to normal, since pyrexia has been demonstrated as being involved in the anaemic process (Karle, 1974; Dargie et al., 1979). Erythrophagocytosis has been demonstrated in natural and experimental T. congolense infections in Blackhead Persian sheep, and is thought to contribute greatly to the severe anaemia during the acute phase of the disease (Mackenzie and Cruickshank, 1973). In chronic cases, however, erythrophagocytosis was not detected. Investigations on experimental T. congolense infections in cattle indicate that the superior resistance of the N’dama breed is primarily due to the ability to limit the height and duration of parasitaemia more efficiently than the Zebu (Dargie et al., 1979). This reasoning may also be applicable to sheep and goats both at the breed and individual level, and may account for the fact that in
TRYPANOSOMIASIS
IN
GOATS
AND
SHEEP
46:J
this study more animals of the indigenous than the exotic breeds were able to effect self-cure and make a good recovery. Unfortunately there is no information on the mechanism of self-cure, but this may be based on individual factors since some animals of both breeds exhibited this phenomenon while others of both breeds succumbed very rapidly. This ability to control parasitac.mia may be related to the capacity of the host to mount a more efIicic.nt immune response (Desowitz, 1959)) and has been demonstrated in inbred strains of mice to be inherited as a dominated trait (Morrison, Roelants. May-Withey and Murray, 1978). It is apparent that sheep and goats may commonly support a 7. congolerw infection for several months with adverse effects on weight gain and production. Chronic infections of this nature may be of equal if not greater importance than the acute fatal diseaseas animals with this syndrome are not only unthrift). and unproductive but may also play a major role in maintaining the disease. cycle in endemic and epizootic areas. SUMMARY
The course of naturally ohserved of Kenya described syndrome
in two breeds over a period on the basis is described in
acquired T@anosoma congolense infections was of sheep and two of goats grazed in an endemic arca of eight months. Three syndromes of‘ the disease arc of the duration of detectable parasitaemia and eacl~ terms of clinical observations. The first two syndromes,
the acute and sub-acute, are sub-divided on the basis of the outcome of the disease, either fatal or self-cure, but the third syndrome, the chronic, invariabl! ended
fatally. ACKNOWLEDGMENTS
We would like to thank the staff of the Kiboko Tsetse Survey and Control Station for their daily cooperation and technical support, and the Director of Veterinary Services for permission to publish. The U.N.D.P./F.A.O. Sheep and Goat Project provided the experimental animals and jointly funded the study. REFERENCES
Dargie, J. D., Murray, P. K., Murray, M., Grimshaw, W. R. T., and McIntyre, the red cell kinetics of N’dama and W. I. M. (1979). Bovine trypanosomiasis: Zebu cattle infected with Trypanosoma congolense. Parasitology. (In Press). Desowitz, R. S. (1959). Studies on immunity and host parasite relationships. 1. The immunological response of resistant and susceptible breeds of cattle to trypanosomal challenge. Annals of Tropical Medicine and Parasitology, 53, 293-313. Finelle, P. (1973). African Animal Trypanosomiasis I. Disease and chemotherapy. World Animal Review, 7, 1-6. Griffin, L. and Allonby, E. W. (1979a). The economic effects of trypanosomiasis in sheep and goats at a range research station in Kenya. Tropical Animal Health and Production. (In Press). Griffin, L. and Allonby, E. W. (1979b). Studies on the epizootiology of trypanosomiasis in sheep and goats in Kenya. Tropical Animal Health and Production. (In Press). Hoare, C. A. (1972). The Trypanosomes of Mammals. Blackwell, Oxford. Ikede, B. 0. and Losos, G. J. (1975). Pathogenesis of T~panosoma brucei infection in sheep. Journal of Comparative Patholopv, 85, 23-31, 33-36, 37-44.
464
L.
GRIFFIN
AND
E.
W.
ALLONBY
Karle,
H. (1974). The pathogenesis of the anaemia of chronic disorders and the role of fever in erythrokinetics. Scandinavian Journal of Haematology, 13, 81-86. Kramer, J. (1966). Incidence of trypanosomiasis in the West African dwarf sheep and goat in Eastern Nigeria. Bulletin of Epirootic Diseases of Africa, 14, 423-428. Losos, G. J. and Ikede, B. 0. (1972). Review of pathology of diseases in domestic and laboratory animals caused by Trypanosoma congolense, 7. vivax, T. brucei, T. rhodesiense and T. gambiense. Veterinary Pathology Suppl. ad., 9. Mackenzie, P. K. I., Boyte, W. P., Nesham, V. N. and Pirie, E. (1978). The aetiology and significance of the phagocytosis of erythrocytes and leucocytes in sheep infected with Trypanosoma congolense. Research in Veterinary Science, 24, 4-7. Mackenzie, P. K. I. and Cruickshank, I. G. (1973). Phagocytosis of erythrocytes and leucocytes in sheep infected with Trypanosoma congolense. Research in Veterinary Science, 15, 256-262. Mahmoud, M. M. and Elmalik, K. H. (1977). Trypanosomiasis: goats as a possible reservoir of Trypanosoma congolense in the Republic of the Sudan. Tropical Animal Health and Production, 9, 167-l 70. Morrison, W. I., Roelants, G. E., May-Withey, Kathleen S. and Murray, M. (1978). Susceptibility of inbred strains of mice to Trypanosoma congolense: correlation with changes in spleen lymphocyte populations. Clinical and Experimental Immunology, 32, 25-40. Stephen, L. E. (1970). Clinical manifestations of the trypanosomiases in livestock and other domestic stock. In The African Trypanosomiases (Ed. H. W. Mulligan). George Allen and Unwin, London, 774-792. [Received for publication,
August 11 th, 19781
PATH.
1979.
DISEASE
YOL.
457
89.
SYNDROMES NATURALLY
IN SHEEP INFECTED
TRY’PANOSOMA
AND WITH
GOATS
CONGOLENSE By
L.
and El
GRIFFIN* Veterinary
W.
Sercices DiziJion,
ALLONBY~ hhbete,
Kensa
INTRODUCTION
Until recently trypanosomiasis was not regarded as an important disease of* sheep and goats. Kramer (1966) reported that the disease in Nigeria was of little importance in these hosts, and Stephen (1970) and Finelle (1973) stated that sheep and goats are seldom infected with trypanosomiasis under natural conditions. However, more recent work indicates that not only are these animals naturally infected by this disease, but that high mortality can OCCUI (Mackenzie and Cruickshank, 1973; Griffin and Allonby, 1979a) and these animals may be important in the transmission of trypanosomiasis to other stock (Mahmoud and Eimalik, 1977). The pathology and pathogenesis of experimental trypanosomiasis in sheep and goats has been studied (Losos and Ikede, 1972; Ikede and Losos, 1975; Mackenzie and Cruickshank, 1973; Mackenzie, Boyte, Nesham and Piric, 1972)) but the various syndromes produced by natural infections have not been clearly described. During an epidemiological study of trypanosomiasis in sheep and goats grazed in an endemic area of Kenya it became apparent that not only are these animals severely affected by trypanosomiasis (Griffin and Allonby, 1979a) but that the disease caused by Tr@anosoma congolense, the only species detected, could be divided into three syndromes based on the duration of detectable parasitaemia. These syndromes produced by the naturally acquired infection are classified and described in this paper. MATERIALS
AND
METHODS
Two breeds of sheep and two breeds of goats, all adult castrates raised in tsetsefree areas were grazed in tsetse-infested rangeland at the Kiboko Range Research Station and the naturally acquired infection was observed for 8 months. Sixteen purebred Galla and 23 Saanen Y Galla crossbred, the first cross between indigenous Galla and the imported Saanen breed, were the goats used. Seventeen local Blackhead Persian and 12 imported Karakul animals were the two breeds of sheep studied. The study area, vegetation, climate, tsetse species and experimental breeds have been described previously (Griffin and Allonby, 1979a). * Present address: P.O. Box 30020, Nairobi, Kenya. t Present address: Animal Health Officer, U.N.D.P.,‘F..\.O. P.0. Box 30218, Nairobi, Kenya. 0021-9975/79/040457+08
$02.00/O
Sheep and Goat
~cs 1979 Xcadcmic
Development
Prejs Ix.
(London)
Project. Limited
458
L.
GRIFFIN
AND
E.
W.
ALLONBY
Packed cell volume (PCV) and rectal temperatures were recorded twice per week, and body weight was measured weekly. Diagnosis of trypanosomiasis was made on the basis of Giemsa stained thick blood smears. RESULTS
The species of trypanosomes detected were classified morphologically according to Hoare (1972). In all cases the species identified was irrypano~oma (Nannamonas) congolense, referred to as T. congolense. Among the breeds of indigenous and exotic sheep and goats naturally infected with T. congolense different patterns of disease emerged which can be divided into three main groups according to the duration of the infection. Within two of these groups another division can be made based on the outcome of the disease, either fatal or “self-cure”, but in the third division the outcome always proved fatal. (1) Acute This was defined as those infections which lasted up to 6 weeks from the first appearance of parasites in a thick blood smear. (a) Fatal. If the outcome was fatal, as exemplified by the clinical data of the case shown in Fig. 1, the disease was characterized by a rapid decrease in PCV to below 15 per cent in some cases. From the time that parasites were detected the body temperature fluctuated widely, at times reaching as high as 41 “C. Due to the rapidity with which death ensued there was very little loss in body weight and the general condition of the animal at death was usually good.
.
30 -
PCV
(%)
L>L-
-
35 30-
\
l -..
l we\
7,,.-/‘lo
25 20-
\ %
28 ;;$
weight 26
24 22 Period of detectable parasltaemia
0
I
I
I
I
I
2
4
6
8
IO
12
14
16
18
Time in weeks
Fig.
1. Clinical data of a goat with of detectable parasitaemia.
a naturally acquired trypanosome Type la Acute, fatal.
infection
in relation
to the period
TRYPANOSOMIASIS
IN
GOATS
AND
-1-59
SHEEP
(b) Self-cure. If not fatal the outcome of the disease was a self-cur? by t hc host after a brief appearance of the parasite in the peripheral blood (Fig. 2). In such cases the temperature was slightly elevated during the period of detectable parasitaemia but returned to normal quite rapidl) when parasites disappeared. The PCV decreased slightly, but rcturncd rapidly to normal, the weight remained steady and there ~vas littlc change in body condition. 40 Body temperature PC)
Rudy (kg)
.
3g
A.,/\
38-o-
/l,e
./‘.-fl
.
A
weight
2. CIinical period
l -.------•
//----.-.-/*’
0
i:ig.
. ,
.
2
4
6
data of a sheep with of detectable parasitaemia.
8
IO
a naturally Type
12 Time acquired 1b Acute.
14 16 in weeks
18
trypanosomr sell-curt.
20
22
inf‘cction
24
26
in rel;ttion
28
to the
12 ) ,Suh-acute This group includes those infections which terminated betwecll 6 and 12 M-eeksafter the initial appearance of parasites. (a) Fatal. In fatal cases the PCV usually showed a marked and stcadv decline early in the infection, as exemplified by the case shown in Fig. 3. and the PCV remained between 15 and 20 per cent for some weeks before death. The temperature showed wide fluctuations from the onsrt of disease between 38.3 “C to 40-O “C. but often remained high for some days immediately prior to death. The weight loss was usually marked at the beginning of the disease, but remained steady latterly, and the host became emaciated, lethargic and its condition poor. (C,; b5’e(f-cure.Those animals which effected a self-cure showed a rapid decrease in PCV with the onset of a detectable parasitaemia. However. the‘ PCV began to increase steadily during the later stages of the disease when the parasitaemia decreased, and reverted rapidly to normal with the disappearance of the parasites (Fig. 4). Thr temperature increased hricfly at the height of diseasebut this was short-lived and it soon dropped to normal. There was usually loss of appetite, and lethargy in the fatal cases, but in those animals which underwent self-cure, rven if the condition of the animal deteriorated initially, it improved with the disappcarancc of the parasites.
460
L.
GRIFFIN
AND
E.
W.
ALLONBY
46 Body (kg)
weight44
/* \
l C.b.
42 Period of detectable parasitaemia 0
2
4
mm 6 Time
Fig. 3. Clinical data of a goat with a naturally acquired of detectable parasitaemia. Type 2a Sub-acute,
Body weight
8 IO in weeks
12
trypanosome fatal.
14
infection
IC
in relation
to the period
35 25 -
Period of detectable parositaemia
e 0
2
4
6
Fig. 4. Clinical data of a goat with of detectable parasitaemia.
8
IO
12
14
I 16 18 20 22 Time in weeks
a naturally acquired Type 2b Sub-acute,
trypanosome self-cure.
1 24
1 26
infection
t 28
t 30
I 32
in relation
I 34
L 3l
to the period
(3) Chronic This category includes all those infections with a parasitaemia lasting over 12 weeks and is exemplified by the clinical data shown in Fig. 5. The parasites were detectable by thick film only intermittently, but nevertheless disappeared and reappeared over a long period. The temperature showed wide fluctuations between 37.7 “C and 40.5 “C and in some cases regular peaks at about 40.5 “C
TRYPANOSOMIASIS
IN
GOATS
AND
461
SHEEP
occurred every 5 or 6 weeks. The PCV showed an initial decline at the onset of infection but remained at 20 to 25 per cent with small fluctuations during the course of the disease, depending on the parasitaemia. The weights showed similar patterns with a decrease followed by a period of steady weight. In all cases the animal became emaciated, the coat dry and staring and the general condition poor, with death as the final outcome.
Body
Body weight (kg)
25 .~~-------*\
20
-/-0..
Fiz%[;io d 0
Fig.
J 2
4
6
8
IO
12
14
16 18 20 22 Time in weeks
5. C:linical data of a sheep with a naturally acquired period of detectable parasitaemia. Type 3 Chronic.
24
26
trypanosome
28
30
32
infection
34
36
in relation
to the.
The number of animals of each breed showing the various syndromes is shown in Table 1. The crossbred goats, the Saanen x Galla and the exotic Karakul sheep showed a higher percentage of deaths out of those becoming infected than the indigenous breeds, 77 and 71.4 per cent compared with 20 and 22 per cent respectively. This is reflected in the larger numbers of infected indigenous animals which effected a self-cure compared with the exotic and crossbred sheep and goats. TABLE
1
$,ndromes Total Breed
number
Saanen x Galla goat Galla goat Karakul sheep Blackhead Persian sheep * Deaths
23 I; 17
JVumber infected
Deaths h’umber (Per cent)*
9 5 7
7 1 5
(20)
9
2
are a percentage
(77)
1. .lcute Fatal
Self-cure
2. Sub-acute Fatal Self-cute
1 2 2
3 0 2
i
(714)
2 0 0
(22.2)
2
3
0
‘l
of the numbers
of infected
animals
in the group.
1
3. C’h~onA
I,
i 3 0
462
L.
GRIFFIN
AND
W.
E.
ALLONBY
DISCUSSION
The disease syndromes in sheep and goats described here conform closely to those described by Mackenzie and Cruickshank (1973) in nine naturally infected Blackhead Persian sheep. They divided the animals into three groups according to the disease pattern observed. Three animals showed an acute infection lasting up to 43 days before death, characterized by a rapid fall in red cell indices, as occurred in Group 1 (a). Animals of their second group showed a chronic infection of 11 and 12 months but terminated by an acute phase immediately before death. This acute phase was not observed in any of the sheep or goats with the chronic or sub-acute infection from Kiboko. However, the sheep described by Mackenzie and Cruickshank (1973) proved to have a mixed infection of T. congolense and T. z&ax, and the latter may have been responsible for the acute phase just before death. These authors also described a third group which showed a protracted course of infection of unspecified duration, but with no acute phase prior to death, and corresponding with Group 3 described in the present study. The apparent self-cure was not described by Mackenzie and Cruickshank (1973) possibly because fewer animals or more virulent strains of parasite were used. Losos (personal communication) described three patterns of disease in cattle experimentally infected with T. congolense, namely acute, chronic and asymptomatic. Cattle in the third group supported a parasitaemia which was high at times, but without showing clinical signs. This was not observed among the naturally infected sheep and goats. If a parasitaemia was detected a reduction in PCV and fluctuation in temperature were also observed. Dargie, Murray, Murray, Grimshaw and McIntyre (1979) demonstrated that in two breeds of cattle, the N’dama and the Zebu experimentally infected with T. congolense, the severity of the disease as monitored by the anaemia was correlated with the height and duration of parasitaemia. Although parasitaemia height could not be determined in this study the presence of parasites in the peripheral circulation was reflected in the change in PCV. However, Dargie et al. (1979) also noted that PCV values showed little tendency to recover even with the disappearance of parasites from the blood. In this study, by contrast, the PCV invariably returned to normal shortly after the disappearance of parasites. This may also be linked to the fact that in these cases the temperature which fluctuated widely during parasitaemic periods also returned to normal, since pyrexia has been demonstrated as being involved in the anaemic process (Karle, 1974; Dargie et al., 1979). Erythrophagocytosis has been demonstrated in natural and experimental T. congolense infections in Blackhead Persian sheep, and is thought to contribute greatly to the severe anaemia during the acute phase of the disease (Mackenzie and Cruickshank, 1973). In chronic cases, however, erythrophagocytosis was not detected. Investigations on experimental T. congolense infections in cattle indicate that the superior resistance of the N’dama breed is primarily due to the ability to limit the height and duration of parasitaemia more efficiently than the Zebu (Dargie et al., 1979). This reasoning may also be applicable to sheep and goats both at the breed and individual level, and may account for the fact that in
TRYPANOSOMIASIS
IN
GOATS
AND
SHEEP
46:J
this study more animals of the indigenous than the exotic breeds were able to effect self-cure and make a good recovery. Unfortunately there is no information on the mechanism of self-cure, but this may be based on individual factors since some animals of both breeds exhibited this phenomenon while others of both breeds succumbed very rapidly. This ability to control parasitac.mia may be related to the capacity of the host to mount a more efIicic.nt immune response (Desowitz, 1959)) and has been demonstrated in inbred strains of mice to be inherited as a dominated trait (Morrison, Roelants. May-Withey and Murray, 1978). It is apparent that sheep and goats may commonly support a 7. congolerw infection for several months with adverse effects on weight gain and production. Chronic infections of this nature may be of equal if not greater importance than the acute fatal diseaseas animals with this syndrome are not only unthrift). and unproductive but may also play a major role in maintaining the disease. cycle in endemic and epizootic areas. SUMMARY
The course of naturally ohserved of Kenya described syndrome
in two breeds over a period on the basis is described in
acquired T@anosoma congolense infections was of sheep and two of goats grazed in an endemic arca of eight months. Three syndromes of‘ the disease arc of the duration of detectable parasitaemia and eacl~ terms of clinical observations. The first two syndromes,
the acute and sub-acute, are sub-divided on the basis of the outcome of the disease, either fatal or self-cure, but the third syndrome, the chronic, invariabl! ended
fatally. ACKNOWLEDGMENTS
We would like to thank the staff of the Kiboko Tsetse Survey and Control Station for their daily cooperation and technical support, and the Director of Veterinary Services for permission to publish. The U.N.D.P./F.A.O. Sheep and Goat Project provided the experimental animals and jointly funded the study. REFERENCES
Dargie, J. D., Murray, P. K., Murray, M., Grimshaw, W. R. T., and McIntyre, the red cell kinetics of N’dama and W. I. M. (1979). Bovine trypanosomiasis: Zebu cattle infected with Trypanosoma congolense. Parasitology. (In Press). Desowitz, R. S. (1959). Studies on immunity and host parasite relationships. 1. The immunological response of resistant and susceptible breeds of cattle to trypanosomal challenge. Annals of Tropical Medicine and Parasitology, 53, 293-313. Finelle, P. (1973). African Animal Trypanosomiasis I. Disease and chemotherapy. World Animal Review, 7, 1-6. Griffin, L. and Allonby, E. W. (1979a). The economic effects of trypanosomiasis in sheep and goats at a range research station in Kenya. Tropical Animal Health and Production. (In Press). Griffin, L. and Allonby, E. W. (1979b). Studies on the epizootiology of trypanosomiasis in sheep and goats in Kenya. Tropical Animal Health and Production. (In Press). Hoare, C. A. (1972). The Trypanosomes of Mammals. Blackwell, Oxford. Ikede, B. 0. and Losos, G. J. (1975). Pathogenesis of T~panosoma brucei infection in sheep. Journal of Comparative Patholopv, 85, 23-31, 33-36, 37-44.
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Karle,
H. (1974). The pathogenesis of the anaemia of chronic disorders and the role of fever in erythrokinetics. Scandinavian Journal of Haematology, 13, 81-86. Kramer, J. (1966). Incidence of trypanosomiasis in the West African dwarf sheep and goat in Eastern Nigeria. Bulletin of Epirootic Diseases of Africa, 14, 423-428. Losos, G. J. and Ikede, B. 0. (1972). Review of pathology of diseases in domestic and laboratory animals caused by Trypanosoma congolense, 7. vivax, T. brucei, T. rhodesiense and T. gambiense. Veterinary Pathology Suppl. ad., 9. Mackenzie, P. K. I., Boyte, W. P., Nesham, V. N. and Pirie, E. (1978). The aetiology and significance of the phagocytosis of erythrocytes and leucocytes in sheep infected with Trypanosoma congolense. Research in Veterinary Science, 24, 4-7. Mackenzie, P. K. I. and Cruickshank, I. G. (1973). Phagocytosis of erythrocytes and leucocytes in sheep infected with Trypanosoma congolense. Research in Veterinary Science, 15, 256-262. Mahmoud, M. M. and Elmalik, K. H. (1977). Trypanosomiasis: goats as a possible reservoir of Trypanosoma congolense in the Republic of the Sudan. Tropical Animal Health and Production, 9, 167-l 70. Morrison, W. I., Roelants, G. E., May-Withey, Kathleen S. and Murray, M. (1978). Susceptibility of inbred strains of mice to Trypanosoma congolense: correlation with changes in spleen lymphocyte populations. Clinical and Experimental Immunology, 32, 25-40. Stephen, L. E. (1970). Clinical manifestations of the trypanosomiases in livestock and other domestic stock. In The African Trypanosomiases (Ed. H. W. Mulligan). George Allen and Unwin, London, 774-792. [Received for publication,
August 11 th, 19781