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Transmission of Anaplasma marginale from a naturally-infected wild african giant rat (Cricetomys gambianus), waterhouse) to a calf in Nigeria
Veterinary Parasitology, 8 (1981) 337--339 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
337
Short Communication TRANSMISSION OF ANAPLASMA MARGINALE FROM A NATURALLY-INFECTED WILD AFRICAN GIANT RAT (CRICETOMYS GAMBIANUS, WATERHOUSE) TO A CALF IN NIGERIA
O.O. DIPEOLU and O.A. AKINBOADE
Department of Veterinary Microbiology and Parasitology, University of Ibadan, Ibadan (Nigeria) A. ADETUNJI
Department of Veterinary Surgery and Reproduction, University of lbadan, Ibadan (Nigeria) (Accepted for publication 23 March 1981 )
ABSTRACT Dipeolu, O.O., Akinboade, O.A. and Adetunji, A., 1981. Transmission of Anaplasma marginale from a naturally-infected wild African giant rat (Cricetomys gambianus, Waterhouse) to a calf in Nigeria. Vet. Parasitol., 8: 337--339. Blood taken from an African giant rat in Nigeria, transmitted Anaplasma marginale when inoculated into a splenectomised calf. The infection of the calf was sub-clinical and the highest percentage of infected erythrocytes recorded was 6. Anaplasma marginale was first observed in the calf's blood three days after inoculation, but the parasite disappeared suddenly, nine days after inoculation. This is the first experimental demonstration of A. marginale infection in African giant rats in Nigeria, a country where anaplasmosis is endemic in the cattle population. The significance of giant rats being a reservoir host of A. marginale in Nigeria is discussed.
INTRODUCTION
In Nigeria, anaplasmosis had been associated with cattle and small ruminants. It had been shown to be of economic importance because of the morbidity and mortality accompanying outbreaks (Folkers and Kuil, 1967; Kuil and Folkers, 1968; Folkers et al., 1970; Dipeolu, 1975). Dipeolu (1975) reported that the disease incidence in Nigerian cattle is higher during the rainy than the dry season. Dipeolu and Ajayi (1975) recorded the presence of A. marginale in the smears made from the blood of wild and semi-wild giant rats captured in Ibadan, a south-western town in Nigeria. In view of the fact that these rodents were clinically healthy despite their high parasitaemia, it was suggested that they may be a reservoir host for the parasite in Nigeria. Further investigations confirmed that a large percentage of wild giant rats from various parts of Nigeria possess varying degrees of parasitaemia with A. 0304-4017/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
338
marginale. This communication reports an a t t e m p t to transfer A. marginale to cattle by the inoculation of blood from a wild giant rat with high parasitaemia into a calf. MATERIALS AND METHODS
Ten ml of blood was obtained from one giant rat which had been caught a few days earlier and found, through blood smears, to possess high parasitaemia with A. marginale (42%). Five ml of the blood was inoculated intravenously into a splenectomised calf and the remaining 5 ml into an unsplenectomised calf, both of which were under 1 year of age. Blood smears for microscopic examination were made on three consecutive occasions before inoculation and on alternate days thereafter for 15 days. The calves were under constant clinical observation and their temperatures were recorded daily from 10 days before inoculation until 15 days after inoculation. The presence of anaplasma infection was determined by finding the organism in the erythrocytes, in the blood smears stained by the Giemsa method. RESULTS
Splenectomised calf The presence of A. marginale was first observed in the calf'.q e r y t h r o c y t e on the 3rd day after inoculation, occurring in about 3% o f the cells. The parasitaemia rose to about 6% of the cells from the 6th day and was maintained until the 9th day post-inoculation, when the parasite suddenly disappeared from the calf's blood. The temperature, which averaged 37.8°C before blood inoculation, rose to 38.1°C one day after and decreased progressively to an average of 37.9° C from the 4th day post-inoculation.
Unsplenectornised calf No A. marginale was found in this calf's erythrocytes t h r o u g h o u t the period of observation. The temperature remained at an average of 37.9°C before and after the blood inoculation. DISCUSSION
The fact t h a t the splenectomised calf became parasitised with A. marginale three days after blood inoculation, and t h a t the parasitaemia persisted for six days thereafter, showed that the parasite was infective to the calf. The temperature recordings, however, showed that the infection was sub-clinical. Christensen and McNeal (1967) obtained a similar result in California when t h e y inoculated blood from a deer into a splenectomised calf.
339
Although only 4% of the red blood cells contained A. marginale in their experiments, the results of their complement fixation test indicated titres comparable with those c o m m o n l y observed in severe infections. The present experiment showed a m a x i m u m of 6% of the red blood cells parasitised with A. marginale b u t no serological tests were performed. The fact that A. marginale infection is latent in the African giant rat and that the transfer through inoculation made it infective, although subclinically, to the splenectomised calf is an indication that this rodent species may be a reservoir host of the parasite in Nigeria. The Savannah, which constitutes a b o u t 75% of the entire trade cattle route, had been shown b y Ajayi (1974) to be the main habitat of giant rats in Nigeria. He described them as Savannah species which colonise large farmland areas of this ecological zone. Hence, the giant rat in Nigeria is in a position to maintain the infection of A. marginale among the trade cattle. Similarly to the deer in California, the African giant rats are nocturnal animals and it is during this time that they are exposed to tick bites. The cattle subsequently graze during the day and could acquire infection with A. marginale from ticks which had previously bitten the giant rats. Further studies on anaplasmosis among African giant rats in the natural state and serological identification of their infection with A. marginale are in progress. ACKNOWLEDGEMENT
This w o r k was done as part of the research grant given by the Federal Ministry of Science and Technology towards the domestication of the giant rat. The authors thank Dr. S.S. Ajayi, of the Department of Forest Resources Management, for support and encouragement to do this work.
REFERENCES Ajayi, S.S., 1974. The biology and domestication of the African giant rat Cricetomys gambianus Waterhouse. Ph.D. Thesis, University of Ibadan. Christensen, J.F. and McNeal, D.W., 1967. Anaplasma marginale infection in deer in the Sierra Nevada foothill area o f California. Am. J. Vet. Res., 28 : 599---601. Dipeolu, O.O., 1975. Survey of blood parasites in domestic animals in Nigeria. Bull. Anita. Health Prod. Aft., 23: 155--164. Dipeolu, O.O. and Ajayi, S.S.~ 1975. The parasites of the African giant rat (Cricetomys gambianus, Waterhouse) in Ibadan, Nigeria. East Afr. Wildl. J., 14: 85--89. Folkers, C. and Kuil, H., 1967. Blood parasites in cattle, sheep and goats in Northern Nigeria. Bull. Epizoot. Dis. Aft., 15: 121. Folkers, C., Buys, J., Blotkamp, J., Van Hoeve, K. and Kuil, H., 1970. Survey of blood parasites of cattle presented for treatment against trypanosomiasis in Nigeria. Bull. Epizoot. Dis. Afr., 18: 215. Kuil, H. and Folkers, C., 1968. Studies on Anaplasma ovis infection. 1. Course of spontaneous infections in splenectomized Nigerian sheep and goats. Bull. Epizoot. Dis. Afr., 16: 65.
337
Short Communication TRANSMISSION OF ANAPLASMA MARGINALE FROM A NATURALLY-INFECTED WILD AFRICAN GIANT RAT (CRICETOMYS GAMBIANUS, WATERHOUSE) TO A CALF IN NIGERIA
O.O. DIPEOLU and O.A. AKINBOADE
Department of Veterinary Microbiology and Parasitology, University of Ibadan, Ibadan (Nigeria) A. ADETUNJI
Department of Veterinary Surgery and Reproduction, University of lbadan, Ibadan (Nigeria) (Accepted for publication 23 March 1981 )
ABSTRACT Dipeolu, O.O., Akinboade, O.A. and Adetunji, A., 1981. Transmission of Anaplasma marginale from a naturally-infected wild African giant rat (Cricetomys gambianus, Waterhouse) to a calf in Nigeria. Vet. Parasitol., 8: 337--339. Blood taken from an African giant rat in Nigeria, transmitted Anaplasma marginale when inoculated into a splenectomised calf. The infection of the calf was sub-clinical and the highest percentage of infected erythrocytes recorded was 6. Anaplasma marginale was first observed in the calf's blood three days after inoculation, but the parasite disappeared suddenly, nine days after inoculation. This is the first experimental demonstration of A. marginale infection in African giant rats in Nigeria, a country where anaplasmosis is endemic in the cattle population. The significance of giant rats being a reservoir host of A. marginale in Nigeria is discussed.
INTRODUCTION
In Nigeria, anaplasmosis had been associated with cattle and small ruminants. It had been shown to be of economic importance because of the morbidity and mortality accompanying outbreaks (Folkers and Kuil, 1967; Kuil and Folkers, 1968; Folkers et al., 1970; Dipeolu, 1975). Dipeolu (1975) reported that the disease incidence in Nigerian cattle is higher during the rainy than the dry season. Dipeolu and Ajayi (1975) recorded the presence of A. marginale in the smears made from the blood of wild and semi-wild giant rats captured in Ibadan, a south-western town in Nigeria. In view of the fact that these rodents were clinically healthy despite their high parasitaemia, it was suggested that they may be a reservoir host for the parasite in Nigeria. Further investigations confirmed that a large percentage of wild giant rats from various parts of Nigeria possess varying degrees of parasitaemia with A. 0304-4017/81/0000--0000/$02.50 © 1981 Elsevier Scientific Publishing Company
338
marginale. This communication reports an a t t e m p t to transfer A. marginale to cattle by the inoculation of blood from a wild giant rat with high parasitaemia into a calf. MATERIALS AND METHODS
Ten ml of blood was obtained from one giant rat which had been caught a few days earlier and found, through blood smears, to possess high parasitaemia with A. marginale (42%). Five ml of the blood was inoculated intravenously into a splenectomised calf and the remaining 5 ml into an unsplenectomised calf, both of which were under 1 year of age. Blood smears for microscopic examination were made on three consecutive occasions before inoculation and on alternate days thereafter for 15 days. The calves were under constant clinical observation and their temperatures were recorded daily from 10 days before inoculation until 15 days after inoculation. The presence of anaplasma infection was determined by finding the organism in the erythrocytes, in the blood smears stained by the Giemsa method. RESULTS
Splenectomised calf The presence of A. marginale was first observed in the calf'.q e r y t h r o c y t e on the 3rd day after inoculation, occurring in about 3% o f the cells. The parasitaemia rose to about 6% of the cells from the 6th day and was maintained until the 9th day post-inoculation, when the parasite suddenly disappeared from the calf's blood. The temperature, which averaged 37.8°C before blood inoculation, rose to 38.1°C one day after and decreased progressively to an average of 37.9° C from the 4th day post-inoculation.
Unsplenectornised calf No A. marginale was found in this calf's erythrocytes t h r o u g h o u t the period of observation. The temperature remained at an average of 37.9°C before and after the blood inoculation. DISCUSSION
The fact t h a t the splenectomised calf became parasitised with A. marginale three days after blood inoculation, and t h a t the parasitaemia persisted for six days thereafter, showed that the parasite was infective to the calf. The temperature recordings, however, showed that the infection was sub-clinical. Christensen and McNeal (1967) obtained a similar result in California when t h e y inoculated blood from a deer into a splenectomised calf.
339
Although only 4% of the red blood cells contained A. marginale in their experiments, the results of their complement fixation test indicated titres comparable with those c o m m o n l y observed in severe infections. The present experiment showed a m a x i m u m of 6% of the red blood cells parasitised with A. marginale b u t no serological tests were performed. The fact that A. marginale infection is latent in the African giant rat and that the transfer through inoculation made it infective, although subclinically, to the splenectomised calf is an indication that this rodent species may be a reservoir host of the parasite in Nigeria. The Savannah, which constitutes a b o u t 75% of the entire trade cattle route, had been shown b y Ajayi (1974) to be the main habitat of giant rats in Nigeria. He described them as Savannah species which colonise large farmland areas of this ecological zone. Hence, the giant rat in Nigeria is in a position to maintain the infection of A. marginale among the trade cattle. Similarly to the deer in California, the African giant rats are nocturnal animals and it is during this time that they are exposed to tick bites. The cattle subsequently graze during the day and could acquire infection with A. marginale from ticks which had previously bitten the giant rats. Further studies on anaplasmosis among African giant rats in the natural state and serological identification of their infection with A. marginale are in progress. ACKNOWLEDGEMENT
This w o r k was done as part of the research grant given by the Federal Ministry of Science and Technology towards the domestication of the giant rat. The authors thank Dr. S.S. Ajayi, of the Department of Forest Resources Management, for support and encouragement to do this work.
REFERENCES Ajayi, S.S., 1974. The biology and domestication of the African giant rat Cricetomys gambianus Waterhouse. Ph.D. Thesis, University of Ibadan. Christensen, J.F. and McNeal, D.W., 1967. Anaplasma marginale infection in deer in the Sierra Nevada foothill area o f California. Am. J. Vet. Res., 28 : 599---601. Dipeolu, O.O., 1975. Survey of blood parasites in domestic animals in Nigeria. Bull. Anita. Health Prod. Aft., 23: 155--164. Dipeolu, O.O. and Ajayi, S.S.~ 1975. The parasites of the African giant rat (Cricetomys gambianus, Waterhouse) in Ibadan, Nigeria. East Afr. Wildl. J., 14: 85--89. Folkers, C. and Kuil, H., 1967. Blood parasites in cattle, sheep and goats in Northern Nigeria. Bull. Epizoot. Dis. Aft., 15: 121. Folkers, C., Buys, J., Blotkamp, J., Van Hoeve, K. and Kuil, H., 1970. Survey of blood parasites of cattle presented for treatment against trypanosomiasis in Nigeria. Bull. Epizoot. Dis. Afr., 18: 215. Kuil, H. and Folkers, C., 1968. Studies on Anaplasma ovis infection. 1. Course of spontaneous infections in splenectomized Nigerian sheep and goats. Bull. Epizoot. Dis. Afr., 16: 65.