Veterinary Microbiology, 22 (1990) 11-16 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
11
Susceptibility of L a b o r a t o r y Animals to E x p e r i m e n t a l Infection with Ife Virus G.O. E Z E I F E K A 1, J.U. U M O H 1, C.D. E Z E O K O L I 2 and N.E. GOMWALK 3
Departments of 1Veterinary Public Health and Preventive Medicine, 2Veterinary Surgery and Medicine, and 3Microbiology, Ahmadu BeUo University, Zaria (Nigeria) (Accepted 9 August 1989)
ABSTRACT Ezeifeka, G.O., Umoh, J.U., Ezeokoli, C.D. and Gomwalk, N.E., 1990. Susceptibility of laboratory animals to experimental infection with Ife virus. Vet. Microbiol., 22: 11-16. The susceptibility of rabbits, domestic chickens and albino rats to experimental infection with Ife virus was investigated. Neither pyrexia nor clinical signs of disease were observed in infected rabbits or chickens. Low-grade viraemia ( 101° mouse lethal doses per 0.02 ml) occurred in intracerebrally (i.c.) inoculated chicks on the second day post-infection. Complement-fixing antibody was detected on the 14th day post-inoculation in rabbits and on the 7th day in chickens. Infant rats < 3 and 5 days of age died after subcutaneous (s.c.) and i.c. inoculation, respectively; older rats survived infection. Ife virus titres were highest in the brain following both i.c. and s.c. inoculation.
INTRODUCTION
Ife virus was originally isolated from the salivary glands, blood and brains of bats (Eidolon helvum) at Ife, and subsequently at Abuja in Nigeria, as well as Saa in the Cameroons in 1971 (Virus Research Laboratory, University of Ibadan, 1971). Ife and Saa are in the Tropical Rain Forest ecological zone whereas Abuja lies in the Southern Guinea Savanna. The virus is an antigenically ungrouped orbivirus, a possible arbovirus, and is unrelated by complement fixation test (CFT) to other members of the genus Orbivirus (Karabatsos, 1985 ). The initial isolation and propagation of Ife virus was in infant mice (Karabatsos, 1985). The susceptibility of other laboratory animals has not been investigated. Complement-fixing antibody against the virus has been found in giant rats (Cricetomys gambianus), Rufous Nile rats (Arvicanthus niloticus) (Ezeifeka et al., 1987) and indigenous domestic ruminants (Ezeifeka et al., 1988). The pathogenicity of Ife virus for these species is not known. In the present study, the susceptibility of laboratory rats, chickens and rabbits to various routes of infection with Ife virus was investigated. 0378-1135/90/$03.50
© 1990 Elsevier Science Publishers B.V.
12
G.O. EZEIFEKAET AL.
MATERIALS AND METHODS
Virus, antigen and control antiserum The virus used in this study was Ife virus strain IBAN57928, originally isolated from bats (E. helvum) at Abuja (Virus Research Laboratory, University of Ibadan, 1971 ) and obtained from Professor O. Tomori, Department of Virology, College of Medicine, University of Ibadan, Nigeria. Virus was propagated by intracerebral (i.c.) inoculation of 2-day-old suckling mice with 0.02 ml of 10% mouse brain suspension of virus in phosphate-buffered saline (PBS, pH 7.2). The final virus stock, a 10% suspension of infected mouse brain in PBS containing 0.75% bovine serum albumin, 100 i.u. m1-1 penicillin and 100 /~g m1-1 streptomycin, was sonicated and filtered through 45-/~m Millipore filters. It contained 104.5 50% mouse lethal doses (MLDso) per 0.02 ml (Reed and Muench, 1938). Antigen was prepared from infected mouse brain by the sucrose-acetone extraction method (Clarke and Casals, 1958) and used at 1% dilution in veronal buffer (pH 7.2). I m m u n e mouse ascitic fluid (IMAF) was prepared as described by Tikasingh et al. (1966). The IMAF was inactivated at 56 °C for 30 min.
Experimental animals Twelve 6-8-week-old rabbits, 45 7-day-old broiler chickens and litters of suckling white albino rats were used in the study. Chickens were not given any vaccines and were maintained on deep litter. Animals were fed on commercial feeds (Pfizer Livestock Feed Ltd., Kaduna, Nigeria) and rabbit rations were supplemented with green vegetables (Amarantus spp. ). Rabbits and chickens were observed for 14 and 7 days, respectively, prior to infection; their blood was screened for the presence of parasites and for contaminating viruses by i.c. inoculation of suckling mice. The presence of antibody against Ife virus was assayed by the CFT in rabbits and rats (Casals, 1967), and the complement fixation inhibition test (CFIT) (Tesh and McCammon, 1979 ) for chicken sera.
Experimental infection Rabbits were divided randomly into two groups of six. Chickens were divided into three groups of 15 each. Four animals from each group of rabbits were inoculated either subcutaneously (s.c.) or intraperitoneally (i.p.) with 1.0 ml of stock containing 5 × 105.5 MLDso of Ife virus. The remaining two animals in each group were inoculated s.c. and i.p. with the same quantity of 10% suspension of normal mouse brain. Ten birds from each group of chickens were also inoculated either i.c., i.p. or s.c. with 0.02 ml of stock containing 105.5 MLDso
SUSCEPTIBILITY OF LABORATORY ANIMALS TO IFE VIRUS
13
of Ife virus. The remaining five birds in each group were inoculated with 0.2 ml of normal mouse brain suspension. Litters of white rats aged between 2 and 7 days were infected i.c., i.p., s.c. or orally with 0.03 ml of stock containing 1.5 × 104.5MLDso of Ife virus. They were observed for 30 days. Blood samples were obtained from rabbits and chickens daily for the first 7 days for viral assay and weekly for serology. Rectal temperatures of chickens and rabbits were taken twice daily throughout the observation period. Virus assay
Ten-fold dilutions of blood samples were made in PBS (pH 7.2 ) containing 0.75% bovine serum albumin, 100 i.u. m1-1 penicillin and 100/tg m1-1 streptomycin. Diluted and undiluted blood samples were assayed for viraemia by i.c. inoculation of 0.02 ml into 2-day-old suckling mice. Tissue samples from experimental animals which died of viral infection were harvested at necropsy and ground in chilled mortars. Five-fold dilutions were made in the same diluent, centrifuged for 5 min at 503 × g and 0.02 ml of supernatant inoculated i.c. into suckling mice. Mice were observed for a 14-day period for signs of illness. Blood and tissue samples were stored a t - 70 ° C and those containing virus were titrated in infant mice; end points were calculated by the method of Reed and Muench (1938). Samples from chickens were assayed for virus in pools of 3-4 samples from the same group. Serological tests
Sera obtained from rabbits on Days 7, 14, 21 and 28, and from rats which survived 21 days post-inoculation, were tested for the presence of antibody against Ife virus by the CFT. Chicken sera obtained on the same days as rabbit sera were tested by the CFIT. Viral isolates were identified by the CFT with specific Ife virus IMAF. RESULTS Rabbits
Neither s.c. nor i.p. inoculation produced overt signs of disease or viraemia in rabbits. No pyrexia was observed in either experimental or control rabbits throughout the observation period. Complement-fixing antibodies appeared in both groups of inoculated rabbits on the 14th day and persisted until the 28th day. Titres were low, at 1/5-1/10.
14
G.O. EZEIFEKAET AL.
Chickens No clinical disease was produced in 7-day-old chickens when infected i.p., s.c. or i.c. with Ife virus. There was no febrile response in the infected chickens. A viraemia of< 101° MLDso per 0.02 ml was observed in i.c. inoculated chickens on the second day post-inoculation. Other routes of inoculation did not produce viraemia. Complement-fixing antibodies were detected on Day 7 postinoculation and had mostly disappeared by Day 28 in both i.c. and i.p. inoculated chicks. No CF antibodies were detected in s.c. inoculated chickens. Titres were again low, 1/5-1/20. Rats Suckling rats 2-5 days of age died after i.e. inoculation with 1.5 × 104.5 MLDso of Ife virus. Average survival time (AST) ranged from 5 days (2-day-old rats ) to 10 days (5-day-old rats) (Table 1 ). Seven-day-old rats survived i.c. inoculation with seroconversion. Rats aged between 2 and 5 days survived i.p. inoculation, but seroconverted. Following s.c. inoculation, 2-3-day-old rats died between 4.5 and 7.0 days. Five-day-old or older rats survived s.c. inoculation with seroconversion (Table 1 ). Rats inoculated i.c. had relatively high virus titres in the brain and the titres decreased with the age of the rats from 108.4 MLD~o per 0.02 ml at 2 days old to 103~ MLDso per 0.02 ml at 5 days old (Table 1). Other organs did not yield virus. When inoculated s.c., virus was detected in the brain at titres of 104.o MLDso per 0.02 ml at 2 days old and 103.4 MLD~o per 0.02 ml at 3 days old (Table 2). Virus was not detected in other organs except for the heart which yielded 101° MLD~o per 0.02 ml of Ife virus. Clinical signs observed in 2-5-dayold rats included restlessness, excitation, biting of the mother's hair coat, pieces of litter or the wire mesh of the cage; convulsions, paralysis and death. TABLE 1 Susceptibility of albino rats to i.e. a n d oral infection with 1.5 × Age of rats Route of (days) infection 2 3 5 7 2 3 5
i.c. i.c. i.e. i.e. Oral Oral Oral
*ND = not done.
Average survival Evidence of time (days) infection
> > > >
4.3 6.5 10.0 21 21 21 21
Paralysis Paralysis Paralysis Survived Survived Survived Survived
10 4.5
B r a i n infectivity CF antibody (MLD~o per 0.02 ml) titre 10 6.4 10 5.6
infection infection infection infection
MLDso of Ire virus
103'~ 0 0 0 0
ND* ND ND 1 : 10 0 0 0
15
SUSCEPTIBILITY OF LABORATORY ANIMALS TO IFE VIRUS
TABLE 2 Susceptibility of albino rats to s.c. and i.p. infection with 1.5 × 104.5MLDsoof Ife virus Age of rats Route of (days) infection
Averagesurvival Evidence of time (days) infection
Brain infectivity CF antibody (MLDs0 per 0.02 ml) titre
2 3 5 2 3 5
4.5 7.0 > 21 > 21 21 21
104.o 103.4 0 0 0 0
s.c. s.c. s.c. i.p. i.p. i.p.
Paralysis and deaths Paralysis and deaths Survived infection Survived infection Survived infection Survived infection
ND* ND 1:5 0 1:5 1:10
*ND = not done. DISCUSSION In this study, Ife virus did not produce overt disease in rabbits or domestic chickens. T h o s e species probably do not play any significant role in the virus transmission cycle. Rabbits, unlike chickens, showed an antibody response to the viral antigens with the development of CF antibody. Albino rats were susceptible to exper i m ent al infection with Ife virus and died after i.c. and s.c. inoculation. Susceptibility to infection by bot h routes was age d e p e n d e n t as rats > 5 a n d > 7 days old survived s.c. and i.c. inoculation, respectively. T h e high titres of virus in the brains of rats following i.c. and s.c. inoculation suggest t h a t Ife virus is neurotropic in young rats. In a survey of 183 wild rodents belonging to six families in K a d u n a State of Nigeria, very high titres of CF antibody against Ife virus were found only in giant rats (C. gambianus) an d Rufous Nile rats (A. niloticus), but no virus was isolated (Ezeifeka et al., 1987). T h e rat family m a y play some role in the epidemiology of the virus. Complement-fixing antibodies were also found in domestic r u m i n a n t species sampled from Sokoto, K a t s i n a and K a d u n a States of Nigeria (Ezeifeka et al., 1988), but the susceptibility of these species to Ife virus is not known. T h e host bat is an edible species and is t r a p p e d for meat in Nigeria, frequently biting the trappers. H u m a n susceptibility to the virus warrants investigation.
REFERENCES Casals, J., 1967. Immunologicaltechniques for animal viruses. In: K. Maramorosch and H. Koprowski (Editors), Methods in Virology,Vol. III. Academic Press, New York, pp. 173-198. Clarke, D.H. and Casals, J., 1958. Techniques for haemagglutination and haemagglutination inhibition with arthropod-borne viruses. Am. J. Trop. Med. Hyg., 7: 561-573. Ezeifeka, G.O., Umoh, J.U., Ezeokoli, C.D. and Ezealor, A.U., 1987. Prevalence of Ife virus infection in wild rodents and birds from Zaria, Nigeria. J. Wildl. Dis., 23: 663-665.
16
G.O.EZEIFEKAET AL.
Ezeifeka, G.O., Umoh, J.U., Ezeokoli, C.D. and Gomwalk, N.E., 1989. Serological evidence of Ire virus infection in Nigerian indigenous domestic ruminants. Trop. Anim. Health Prod., 21:55 57. Karabatsos, N., 1985. International catalogue of arboviruses including certain other viruses of vertebrates. American Society of Tropical Medicine and Hygiene, San Antonio, TX, 1147 pp. Reed, L.T. and Muench, H., 1938. A simple method of estimating fifty percent end points. Am. J. Trop. Med. Hyg., 27: 493. Tesh, M.J. and McCammon, J.R., 1979. Detection of arbovirus antibodies in avian sera by the complement fixation inhibition test. Am. J. Vet. Res., 40: 299-301. Tikasingh, E.S., Spence, L. and Downs, W.G., 1966. The use of adjuvant and sarcoma 180 cells in the production of mouse hyperimmune ascitic fluids to arboviruses. Am. J. Trop. Med. Hyg., 15: 219-226. Virus Research Laboratory, University of Ibadan, Ibadan, Nigeria, 1971. Annual Report, pp. 3132.
11
Susceptibility of L a b o r a t o r y Animals to E x p e r i m e n t a l Infection with Ife Virus G.O. E Z E I F E K A 1, J.U. U M O H 1, C.D. E Z E O K O L I 2 and N.E. GOMWALK 3
Departments of 1Veterinary Public Health and Preventive Medicine, 2Veterinary Surgery and Medicine, and 3Microbiology, Ahmadu BeUo University, Zaria (Nigeria) (Accepted 9 August 1989)
ABSTRACT Ezeifeka, G.O., Umoh, J.U., Ezeokoli, C.D. and Gomwalk, N.E., 1990. Susceptibility of laboratory animals to experimental infection with Ife virus. Vet. Microbiol., 22: 11-16. The susceptibility of rabbits, domestic chickens and albino rats to experimental infection with Ife virus was investigated. Neither pyrexia nor clinical signs of disease were observed in infected rabbits or chickens. Low-grade viraemia ( 101° mouse lethal doses per 0.02 ml) occurred in intracerebrally (i.c.) inoculated chicks on the second day post-infection. Complement-fixing antibody was detected on the 14th day post-inoculation in rabbits and on the 7th day in chickens. Infant rats < 3 and 5 days of age died after subcutaneous (s.c.) and i.c. inoculation, respectively; older rats survived infection. Ife virus titres were highest in the brain following both i.c. and s.c. inoculation.
INTRODUCTION
Ife virus was originally isolated from the salivary glands, blood and brains of bats (Eidolon helvum) at Ife, and subsequently at Abuja in Nigeria, as well as Saa in the Cameroons in 1971 (Virus Research Laboratory, University of Ibadan, 1971). Ife and Saa are in the Tropical Rain Forest ecological zone whereas Abuja lies in the Southern Guinea Savanna. The virus is an antigenically ungrouped orbivirus, a possible arbovirus, and is unrelated by complement fixation test (CFT) to other members of the genus Orbivirus (Karabatsos, 1985 ). The initial isolation and propagation of Ife virus was in infant mice (Karabatsos, 1985). The susceptibility of other laboratory animals has not been investigated. Complement-fixing antibody against the virus has been found in giant rats (Cricetomys gambianus), Rufous Nile rats (Arvicanthus niloticus) (Ezeifeka et al., 1987) and indigenous domestic ruminants (Ezeifeka et al., 1988). The pathogenicity of Ife virus for these species is not known. In the present study, the susceptibility of laboratory rats, chickens and rabbits to various routes of infection with Ife virus was investigated. 0378-1135/90/$03.50
© 1990 Elsevier Science Publishers B.V.
12
G.O. EZEIFEKAET AL.
MATERIALS AND METHODS
Virus, antigen and control antiserum The virus used in this study was Ife virus strain IBAN57928, originally isolated from bats (E. helvum) at Abuja (Virus Research Laboratory, University of Ibadan, 1971 ) and obtained from Professor O. Tomori, Department of Virology, College of Medicine, University of Ibadan, Nigeria. Virus was propagated by intracerebral (i.c.) inoculation of 2-day-old suckling mice with 0.02 ml of 10% mouse brain suspension of virus in phosphate-buffered saline (PBS, pH 7.2). The final virus stock, a 10% suspension of infected mouse brain in PBS containing 0.75% bovine serum albumin, 100 i.u. m1-1 penicillin and 100 /~g m1-1 streptomycin, was sonicated and filtered through 45-/~m Millipore filters. It contained 104.5 50% mouse lethal doses (MLDso) per 0.02 ml (Reed and Muench, 1938). Antigen was prepared from infected mouse brain by the sucrose-acetone extraction method (Clarke and Casals, 1958) and used at 1% dilution in veronal buffer (pH 7.2). I m m u n e mouse ascitic fluid (IMAF) was prepared as described by Tikasingh et al. (1966). The IMAF was inactivated at 56 °C for 30 min.
Experimental animals Twelve 6-8-week-old rabbits, 45 7-day-old broiler chickens and litters of suckling white albino rats were used in the study. Chickens were not given any vaccines and were maintained on deep litter. Animals were fed on commercial feeds (Pfizer Livestock Feed Ltd., Kaduna, Nigeria) and rabbit rations were supplemented with green vegetables (Amarantus spp. ). Rabbits and chickens were observed for 14 and 7 days, respectively, prior to infection; their blood was screened for the presence of parasites and for contaminating viruses by i.c. inoculation of suckling mice. The presence of antibody against Ife virus was assayed by the CFT in rabbits and rats (Casals, 1967), and the complement fixation inhibition test (CFIT) (Tesh and McCammon, 1979 ) for chicken sera.
Experimental infection Rabbits were divided randomly into two groups of six. Chickens were divided into three groups of 15 each. Four animals from each group of rabbits were inoculated either subcutaneously (s.c.) or intraperitoneally (i.p.) with 1.0 ml of stock containing 5 × 105.5 MLDso of Ife virus. The remaining two animals in each group were inoculated s.c. and i.p. with the same quantity of 10% suspension of normal mouse brain. Ten birds from each group of chickens were also inoculated either i.c., i.p. or s.c. with 0.02 ml of stock containing 105.5 MLDso
SUSCEPTIBILITY OF LABORATORY ANIMALS TO IFE VIRUS
13
of Ife virus. The remaining five birds in each group were inoculated with 0.2 ml of normal mouse brain suspension. Litters of white rats aged between 2 and 7 days were infected i.c., i.p., s.c. or orally with 0.03 ml of stock containing 1.5 × 104.5MLDso of Ife virus. They were observed for 30 days. Blood samples were obtained from rabbits and chickens daily for the first 7 days for viral assay and weekly for serology. Rectal temperatures of chickens and rabbits were taken twice daily throughout the observation period. Virus assay
Ten-fold dilutions of blood samples were made in PBS (pH 7.2 ) containing 0.75% bovine serum albumin, 100 i.u. m1-1 penicillin and 100/tg m1-1 streptomycin. Diluted and undiluted blood samples were assayed for viraemia by i.c. inoculation of 0.02 ml into 2-day-old suckling mice. Tissue samples from experimental animals which died of viral infection were harvested at necropsy and ground in chilled mortars. Five-fold dilutions were made in the same diluent, centrifuged for 5 min at 503 × g and 0.02 ml of supernatant inoculated i.c. into suckling mice. Mice were observed for a 14-day period for signs of illness. Blood and tissue samples were stored a t - 70 ° C and those containing virus were titrated in infant mice; end points were calculated by the method of Reed and Muench (1938). Samples from chickens were assayed for virus in pools of 3-4 samples from the same group. Serological tests
Sera obtained from rabbits on Days 7, 14, 21 and 28, and from rats which survived 21 days post-inoculation, were tested for the presence of antibody against Ife virus by the CFT. Chicken sera obtained on the same days as rabbit sera were tested by the CFIT. Viral isolates were identified by the CFT with specific Ife virus IMAF. RESULTS Rabbits
Neither s.c. nor i.p. inoculation produced overt signs of disease or viraemia in rabbits. No pyrexia was observed in either experimental or control rabbits throughout the observation period. Complement-fixing antibodies appeared in both groups of inoculated rabbits on the 14th day and persisted until the 28th day. Titres were low, at 1/5-1/10.
14
G.O. EZEIFEKAET AL.
Chickens No clinical disease was produced in 7-day-old chickens when infected i.p., s.c. or i.c. with Ife virus. There was no febrile response in the infected chickens. A viraemia of< 101° MLDso per 0.02 ml was observed in i.c. inoculated chickens on the second day post-inoculation. Other routes of inoculation did not produce viraemia. Complement-fixing antibodies were detected on Day 7 postinoculation and had mostly disappeared by Day 28 in both i.c. and i.p. inoculated chicks. No CF antibodies were detected in s.c. inoculated chickens. Titres were again low, 1/5-1/20. Rats Suckling rats 2-5 days of age died after i.e. inoculation with 1.5 × 104.5 MLDso of Ife virus. Average survival time (AST) ranged from 5 days (2-day-old rats ) to 10 days (5-day-old rats) (Table 1 ). Seven-day-old rats survived i.c. inoculation with seroconversion. Rats aged between 2 and 5 days survived i.p. inoculation, but seroconverted. Following s.c. inoculation, 2-3-day-old rats died between 4.5 and 7.0 days. Five-day-old or older rats survived s.c. inoculation with seroconversion (Table 1 ). Rats inoculated i.c. had relatively high virus titres in the brain and the titres decreased with the age of the rats from 108.4 MLD~o per 0.02 ml at 2 days old to 103~ MLDso per 0.02 ml at 5 days old (Table 1). Other organs did not yield virus. When inoculated s.c., virus was detected in the brain at titres of 104.o MLDso per 0.02 ml at 2 days old and 103.4 MLD~o per 0.02 ml at 3 days old (Table 2). Virus was not detected in other organs except for the heart which yielded 101° MLD~o per 0.02 ml of Ife virus. Clinical signs observed in 2-5-dayold rats included restlessness, excitation, biting of the mother's hair coat, pieces of litter or the wire mesh of the cage; convulsions, paralysis and death. TABLE 1 Susceptibility of albino rats to i.e. a n d oral infection with 1.5 × Age of rats Route of (days) infection 2 3 5 7 2 3 5
i.c. i.c. i.e. i.e. Oral Oral Oral
*ND = not done.
Average survival Evidence of time (days) infection
> > > >
4.3 6.5 10.0 21 21 21 21
Paralysis Paralysis Paralysis Survived Survived Survived Survived
10 4.5
B r a i n infectivity CF antibody (MLD~o per 0.02 ml) titre 10 6.4 10 5.6
infection infection infection infection
MLDso of Ire virus
103'~ 0 0 0 0
ND* ND ND 1 : 10 0 0 0
15
SUSCEPTIBILITY OF LABORATORY ANIMALS TO IFE VIRUS
TABLE 2 Susceptibility of albino rats to s.c. and i.p. infection with 1.5 × 104.5MLDsoof Ife virus Age of rats Route of (days) infection
Averagesurvival Evidence of time (days) infection
Brain infectivity CF antibody (MLDs0 per 0.02 ml) titre
2 3 5 2 3 5
4.5 7.0 > 21 > 21 21 21
104.o 103.4 0 0 0 0
s.c. s.c. s.c. i.p. i.p. i.p.
Paralysis and deaths Paralysis and deaths Survived infection Survived infection Survived infection Survived infection
ND* ND 1:5 0 1:5 1:10
*ND = not done. DISCUSSION In this study, Ife virus did not produce overt disease in rabbits or domestic chickens. T h o s e species probably do not play any significant role in the virus transmission cycle. Rabbits, unlike chickens, showed an antibody response to the viral antigens with the development of CF antibody. Albino rats were susceptible to exper i m ent al infection with Ife virus and died after i.c. and s.c. inoculation. Susceptibility to infection by bot h routes was age d e p e n d e n t as rats > 5 a n d > 7 days old survived s.c. and i.c. inoculation, respectively. T h e high titres of virus in the brains of rats following i.c. and s.c. inoculation suggest t h a t Ife virus is neurotropic in young rats. In a survey of 183 wild rodents belonging to six families in K a d u n a State of Nigeria, very high titres of CF antibody against Ife virus were found only in giant rats (C. gambianus) an d Rufous Nile rats (A. niloticus), but no virus was isolated (Ezeifeka et al., 1987). T h e rat family m a y play some role in the epidemiology of the virus. Complement-fixing antibodies were also found in domestic r u m i n a n t species sampled from Sokoto, K a t s i n a and K a d u n a States of Nigeria (Ezeifeka et al., 1988), but the susceptibility of these species to Ife virus is not known. T h e host bat is an edible species and is t r a p p e d for meat in Nigeria, frequently biting the trappers. H u m a n susceptibility to the virus warrants investigation.
REFERENCES Casals, J., 1967. Immunologicaltechniques for animal viruses. In: K. Maramorosch and H. Koprowski (Editors), Methods in Virology,Vol. III. Academic Press, New York, pp. 173-198. Clarke, D.H. and Casals, J., 1958. Techniques for haemagglutination and haemagglutination inhibition with arthropod-borne viruses. Am. J. Trop. Med. Hyg., 7: 561-573. Ezeifeka, G.O., Umoh, J.U., Ezeokoli, C.D. and Ezealor, A.U., 1987. Prevalence of Ife virus infection in wild rodents and birds from Zaria, Nigeria. J. Wildl. Dis., 23: 663-665.
16
G.O.EZEIFEKAET AL.
Ezeifeka, G.O., Umoh, J.U., Ezeokoli, C.D. and Gomwalk, N.E., 1989. Serological evidence of Ire virus infection in Nigerian indigenous domestic ruminants. Trop. Anim. Health Prod., 21:55 57. Karabatsos, N., 1985. International catalogue of arboviruses including certain other viruses of vertebrates. American Society of Tropical Medicine and Hygiene, San Antonio, TX, 1147 pp. Reed, L.T. and Muench, H., 1938. A simple method of estimating fifty percent end points. Am. J. Trop. Med. Hyg., 27: 493. Tesh, M.J. and McCammon, J.R., 1979. Detection of arbovirus antibodies in avian sera by the complement fixation inhibition test. Am. J. Vet. Res., 40: 299-301. Tikasingh, E.S., Spence, L. and Downs, W.G., 1966. The use of adjuvant and sarcoma 180 cells in the production of mouse hyperimmune ascitic fluids to arboviruses. Am. J. Trop. Med. Hyg., 15: 219-226. Virus Research Laboratory, University of Ibadan, Ibadan, Nigeria, 1971. Annual Report, pp. 3132.
