THE PATHOGENICITY OF AN ISOLATE OF INFECTIOUS BURSAL DISEASE VIRUS IN GUINEA FOWLS

Five weeks old guinea fowls were inoculated intraocularly with a 20% bursal suspension containing a local Nigerian isolate of infectious burfa! disease virus (IBDV) which had a bursal lesion titre of 10· per 0.5 mI. No clinical signs were observed. Gross lesions were absent and microscopic lesions were not found in the bursa, spleen and kidney on days 3 and 5 post infection (PI). IBDV antigen was not detected in the bursa. Tests for IBDV precipitins in serum samples obtained on day 14 PI were also negative.

Five weeks old guinea fowls were inoculated intraocularly with a 20% bursal suspension containing a local Nigerian isolate of infectious burfa!disease virus (IBDV) which had a bursal lesion titre of 10• per 0.5 mI.No clinical signs were observed.Gross lesions were absent and microscopic lesions were not found in the bursa, spleen and kidney on days 3 and 5 post infection (PI).IBDV antigen was not detected in the bursa.Tests for IBDV precipitins in serum samples obtained on day 14 PI were also negative.
Infectious bursal disease (IBD) is mainly a disease of domestic fowl (0 k 0 Y e 1984) .However, there is still limited information on the susceptibility of some avian species to IBDV infection.This paper describes the pathogenicity of an isolate of IBDV in guinea fowls.

Flo c k h i s t o r y and I B 0 V
The IBDV was obtained as a 20% suspension, in phosphate buffered saline (PBS), of the bursa of chickens that died Qf outbreaks of IBD confirmed by methods already described by 0 k 0 y e and U Z 0 u k w u (1981).Thfi 5 suspension was found to contain bursal lesion (BL 50 ) titre of 10 • /0.5 ml by method of R e e d and M u e n c h (1938).
The guinea fowls were obtained at one day of agEand brooded by the deep litter system.At 5 weeks of age they were divided into 2 groups (A and B), placed in cages and housed separately.Group A fowls were each given a total of 0.05 ml of the bursal suspension in the 2 eyes.Group B birds were each similarly treated with 20% normal bursal suspension in PBD (uninfected control).

E x ami nat ion
Pat h 0 log i cal for C l i n i c a l C han g e s and Both groups were observed twice daily for clinical signs.On days 3 and 5 post infection (PI) 3 infected and 2 control birds were sacrificed and examined for gross lesions.The weights of the carcass and bursa were obtained for each bird and the bursal % of carcass weight was determined.The bursa, spleen and kidney of the birds were prepared for histopathology.E x ami nat ion for I BOa n t i g e n i n t h e bur s a Bursas of birds sacrificed in both groups on days 3 and 5 PI were suspended with equivalent weight/volume of PBS to make a 50% suspension.The suspension was tested for IBDV antigen by agar gel diffusion precipitation test (AGDT) using the method and agar described by 0 k 0 y e and U Z 0 u k w u (1981).
E x ami nat ion f•o r I B 0 V pre c i p i t ins Blood was collected from 5 of the guinea fowls at day 0 before infection, from 5 infected and 5 uninfected 14 days PI.Sera were harvested and inactivated at 56•C for 30 min..The samples were tested for IBDV precipitins in AGDT as described above.

Discussion
Reports of experimental infection of guinea fowls with IBDV appear to be scarce.But N a w a the et ale (1978) and 0 k 0 Y e (1988) after serological surveys of guinea fowl farms by AGP~T found no evidence of IBDV infection in the birds.The ' .clinical and pathological results of this investigation.indicate that IBDV may not be pathogenic to guinea fowls.AGDT has been found less sensitive than virus isolation, fluorescent antibody test, serum neutralization test and enzyme-linked immunosorbent assay in detecting IBDV infection (I d e 1975; Ma r q ua r d t et al. 1980; How i e and Tho r sen 1981; p'" h i I l i p s 1981).Hence more work is needed to determine if the birds are completely resistant to IBDV infection.
Guinea fowls exist in the wild and are often reared in the same premises or areas with susceptible chickens.It is therefore necessary to determine if they play any role in the spread of the disease to chickens.