O. Bwangamoi and C.P. Otim
Animal Health Research Centre,
P.O. Box 24,
Entebbe,
Uganda.
Clexon, a trade name for parvaquone is an analogue for menoctone which had earlier been identified as having anti-theilerial activity against Theileria parva in vitro (McHardy, Haigh and Dolan, 1976) and in vivo (Mchardy et al., 1976; Dolan and McHardy, 1978). Unfortunately menoctone was found expensive and complex to synthesise and was not developed. Parvaquone, an active analogue of menoctone, was later shown to control tick stabilate induced infections of T.parva (East Coast Fever) with a single treatment of 20 mg/kg of body weight and was chosen for development (McHardy, Hudson and Rae, 1960).
In a recent trial in Kenya, 92% cattle with East Coast Fever (ECF) recovered after treatment with parvaquone (Wellcome Kenya Limited). The conclusion drawn from that the field trial in Kenya was that parvaquone could be effectively used to treat ECF especially, when the disease was diagnosed early in the febrile state.
The purpose of this trial was to find out the effectiveness of Clexon to different field strains of T.parva in Uganda.
There were two types of field treatment trials carried out. One involved experimentally induced ECF and the other, natural field infection in Gulu, Mukono, Kampala, Entebbe and Masaka areas.
(1) Experimental ECF in Gulu:
35 Boran crosses aged between 6 to 12 months were purchased from Uganda Livestock Industries Ranch, Aswa, Kitgum District. There were 15 heifers, 7 bulls and 13 steers. The cattle were walked from Aswa Ranch to Palm Rivers Farm, Opidi, Koch Ongako Division, Gulu District, 50 miles away. Palm Rivers Farm, located 20 kilometers west of Gulu Town, covers an area of 600 hectares. It is divided into two equal halves so that grazing is confined to the northern half. The vegetation is high savannah with various species of grass, some growing to 2 metres in height. At the time when the experimental animals arrived in the month of September 1983, the grass had reached full maturity except in patches where the cattle (approximately 60 heads) and wild animals (reedbuck, bushbuck, dikdik and warthog) had kept it down. There are 13 branches of the River Ayago with running water within the space of 300 hectares. Along the course of the larger tributaries, namely Angica, Ogok, Bakmokc, and Pem-matidi there are clumps of trees and even small forests. The grazing area had been fenced only at the perimeter. It was known that a highly fatal strain of ECF existed at Palm Rivers because of 25 heads of cattle (Borans and crosses of Dairy Shorthorn, Hereford and Friesians), which were acquired from Acholi Ranch, Aswa in March of 1979, 8 perished in two weeks of ECP because the Liberation War blocked supply of acaricides.
On arrival, the animals were put to graze on pasture infested with ticks. They were not washed in acaricide until they caught ECF when they were hand-sprayed with Delnav DFF once a week. The application of Delnav was continued indefinitely or until the beast died. Diagnosis of ECF was made when the rectal temperature was found to be 39.50C or above and T.parva piroplasms and schizonts were seen in Giemsa stained blood or lymph node smears respectively. Twenty-eight out of the 35 infected cattle (5 bulls, 11 steers and 12 heifers) were treated with Clexon at the dose rate of 10 mg/kg body weight and treatment was repeated 48 hours later with the same dose except in the case of eight beasts (3 bulls, 3 steers and 2 heifers) which received a single injection (contrary to experimental design) because as soon as they fell sick, they hid in the thicket where 6 of them were found dead on the day when they should have received the second injection, but two got lost and the bones were found when the grass burnt during the dry season. The remaining 7 cattle were not treated and so acted as controls (Table 1).
Table 1: Experimental Infection of Cattle from Aswa
SEX |
TREATED |
UNTREATED |
TOTAL |
Bulls |
5 |
2 |
7 |
Steers |
11 |
2 |
13 |
Heifers |
12 |
3 |
15 |
|
TOTAL |
28 |
7 |
35 |
Cattle which naturally contracted ECF in the vicinity of the towns of Gulu, Mukono, Kampala, Entebbe and Masaka (and were reported to us by the owners) were treated with Clexon after confirmation of diagnosi5; as above. There were altogether 69 head of cattle treated and three served a& controls in those areas in Gulu area the cattle treated were all Zebu type aged between 4 and 12 months except one Boran cross; bull calf. In Mukono, Kampala and Entebbe all cattle were adult Friesian; in Masaka the majority were adult Boran heifers, in addition to 5 Ankole Longhorn calves.
There were 97 cattle treated altogether with Clexon and 78.411 survived ECF; however the results differed between experimental find natural infection.
In all 46.4% survived ECF after treatment with Clexon as sholin in Table 2.
Table 2: Response to Treatment on Experimental Cattle from Aswa.
SEX |
TREATED |
DEAD |
LOST/DEAD |
SURVIVED |
Bull |
5 |
2 |
1 |
2 |
Steer |
11 |
9 |
0 |
2 |
Heifer |
12 |
2 |
1 |
9 |
TOTAL |
28 |
13 |
2* |
13** (46.43%) |
* Bones found during following dry season after grass burned
** Still not all became solidly immune; 6 of these 13 died of ECF several months after the experiment was concluded
28.6% of the animals that had to be treated received only one dose, instead of two, and all died. Of the 20 cattle that received the recommended two treatments i.e. full dosage, 65% survived ECF. All the untreated cattle acting as controls died of ECF.
91.3% of all cattle treated after natural infection survived ECF. The results varied from place to place, such as 94.1% in Gulu, 100% in Kampala, Mukono and Entebbe and 86.6% in Masaka as shown in
Tables 3, 4 and 5.
Table 3: Response to Treatment of Farm Cattle - Gulu
|
SEX |
TREATED |
DEAD |
SLAUGHTERED |
SURVIVED |
Bull |
17 |
1* |
0 |
16 |
Steer |
16 |
0 |
0 |
16 |
Heifer |
1 |
0 |
1 |
0 |
TOTAL |
34 |
1 |
1 |
32=94.12% |
*After 1 month
Table 4: Response to Treatment of Farm Cattle: Kampala, Mukono and Entebbe
|
SEX |
TREATED |
DIED |
SURVIVED |
Bull |
1 |
0 |
1 |
Steer |
3 |
0 |
3 |
Heifer |
1 |
0 |
1 |
Total |
5 |
0 |
5=100% |
Table 5: Response to Treatment of Farm Cattle - Masaka
BREED |
TREATED |
DIED |
SURVIVED |
UNTREATED |
DIED |
SURVIVED |
Boran |
24 |
3 |
21 |
3 |
3 |
0 |
Boran-Cross |
1 |
1 |
0 |
0 |
0 |
0 |
Ankole |
5 |
0 |
5 |
0 |
0 |
0 |
TOTAL |
30 |
4 |
26 (87%) |
3 |
3 |
0 |
There was no difference in response to treatment in breed, age and sex. The 4 cattle which died in Masaka had been given one treatment only and were in the advanced stages of ECF. Death occurred within twelve hours of the first treatment. All the untreated cattle died of ECF.
78.4% of all animals treated with Clexon survived ECF. However the response was better on individual farms where 91.3% of the cattle survived as opposed to only 46.4% in experimental animals. The reasons for this marked difference was partly due to the fact that in the latter case, 8 beasts hid themselves in the bush after. only a single dose of 10 mg/kg body weight. McHardy et al. (1980) showed that a single injection was effective at 20 mg/kg body weight and it was recommended that the dose be divided into two and be given 46 hours apart. This is supported by the fact that a much higher rate of survival, 65%, was obtained when the experimental cattle were injected twice. Other contributory causes to the poor performance of the cattle from Aswa was fatigue. They walked a distance of 80 kilometers and on arrival were immediately challenged to a high dose of a virulent strain of ECF through the numerous ticks which parasitized them. Add to that, the pasture was poor because the grass, mainly Hyperaenia spp was fully mature and thus lignified. Such adverse conditions must have contributed to the lowering of the resistance of the Aswa cattle. In contrast to that, the field cases occurred on individual farms where the cattle had long been acclimatised and the conditions under which they lived were more conclusive to recovery. The recovery of 91% of the farm cattle after treatment with Clexon compares favourably with that obtained in Kenya (92%).
This trial showed that Clexon is effective for treatment of ECF caused by different strains of Theileria parva in Uganda. However a further trial is necessary to show its potential under harsh conditions such as experienced at Palm Rivers Farm, Opidi.
The authors are grateful to Mr. G.M. Odeke, Senior Laboratory Technologist and Mr. Walter Obua, Laboratory Assistant for assisting in the management of the experimental animals. Funds, chemical's, reagents and drugs for this work was supplied by Wellcome (K) Limited.
Dolan, T.T. and McHardy, N. (1978). In: "Tick-borne Diseases and their vectors". (Wilde, J.K.H. ed.) pp. 318 University of Edinburgh.
McHardy, N., Haigh, A.J.B. and Dolan, T.T. (1976). Nature 261, 698
McHardy, N., Hudson, A.T. and Rae, D.G. (1980). In: "The in vitro cultivation of pathogens of tropical diseases". p. 149 Schwabe & Co., Basel.
