ACTA VET .BRNO.55.1986: 207-2119 SEROLOGICAL EVIDENCE OF INFECTIOUS BURSAL DISEASE VIRUS INFECTION IN WILD RATS

Ok 0 y e J. O. A., U c he U. E.: S~ologieal Evidenee 06 In6ecUo1L6 8wL.\a.t. VLlelMle VLw.6 In6ecUon in Wad Rw. Acta Vet. Brno. 55, 1986: 207-209. A total of 23 wild rats (Rattu6 ~) were caught dead by traps set in 4 different poultry farms with history of outbreak of infectious bursal disease (IBD). The internal. organs were suspended in phosphate buffered saline (PBS) and assayed for IBD precipitins and antigens by agar gel diffusion precipitation test (AGDT). Six samples were positive for precipitins. These observations indicate that IBD virus multiples in wild rats and these rats may play some role in the spread of the disease among poultry farms. Ep-izoouology, 4cJleeMng, IUJdew. Infectious bursal disease (IBD) of chickens was first described in United States of America by Cos g r 0 v e (1962). O'n u n k w 0 (1975) confirmed the existence of the disease in Nigeria. Further s~udies by N a w a the et a1. (1978), 0 nun k w 0 (1978), 0 k 0 Y e and U z 0 uk w u (1982) showed that IBD is not only endemic but also causes an unusually/hign mortality in Nigeria. But the epizootology of the disease is not well understood. It has been observed that once IBD enters a farm, it reoccurs in subsequent flocks (C e s s i and G u a 1 and i 1977; Sam b erg and K e r 0 Z 1977; Tho r n ton 1977; 0 k 0 Y e and U z 0 u k w u 1982). This reoccurrence could be due to the persistence of IBD virus in infected farms (V i n d e v 0 gel et al. 1976) due to the physical and chemical properties of the virus (P e t e k et al. 1973). The disease primarily affects the domestic fowl (0 k 0 Y e 1984) but the experimental form has been described in mice by R ina 1 diet al. (1970), Cam mar a t a et al. (1979) and Be s t e t t 0 et al. (1980). Not much is known about the ability of IBD virus to infect wild rats (Rattu6 ~) which commonly inhabit poultry houses and can act as disease carriers. Some of these rats live in the bush and go into the farms in the night to eat the feeds kept in the feeders and in the stores. Often chicks are eaten by these rats. Material and Methods Over a period of 3 months, 23 wild rats were caught dead with traps set in 4 different farms with history of outbreaks of IBD in chickens. Each rat was eviscerated and the lungs, liver, kidney. heart and spleen were collectively weighed and homogenized with equivalent volume/weight of phosphate buffered saline (PBS). The homogenates were assayed for IBD virus precipitins and antigens in agar gel diffusion precipitation test (AGDT) using the agar and method described by Ok 0 Y e and U z 0 u k w u (1981). For detection of precipitins. the positive control was known IBD antiserum and negative control was normsl serum. In antigen detection, the positive control was a suspension of infected bursa while the negative control was normsl bursal suspension. ,.

by traps set in 4 different poultry farms with history of outbreak of infectious bursal disease (IBD).The internal.organs were suspended in phosphate buffered saline (PBS) and assayed for IBD precipitins and antigens by agar gel diffusion precipitation test (AGDT).Six samples were positive for precipitins.These observations indicate that IBD virus multiples in wild rats and these rats may play some role in the spread of the disease among poultry farms.
Infectious bursal disease (IBD) of chickens was first described in United States of America by Cos g r 0 v e (1962).O'n u n k w 0 (1975) confirmed the existence of the disease in Nigeria.Further s~udies by N a w a the et a1.(1978), 0 nun k w 0 (1978), 0 k 0 Y e and U z 0 uk w u (1982) showed that IBD is not only endemic but also causes an unusually/hign mortality in Nigeria.But the epizootology of the disease is not well understood.(1980).Not much is known about the ability of IBD virus to infect wild rats (Rattu6 ~) which commonly inhabit poultry houses and can act as disease carriers.Some of these rats live in the bush and go into the farms in the night to eat the feeds kept in the feeders and in the stores.Often chicks are eaten by these rats.

Material and Methods
Over a period of 3 months, 23 wild rats were caught dead with traps set in 4 different farms with history of outbreaks of IBD in chickens.Each rat was eviscerated and the lungs, liver, kidney.heart and spleen were collectively weighed and homogenized with equivalent volume/weight of phosphate buffered saline (PBS).The homogenates were assayed for IBD virus precipitins and antigens in agar gel diffusion precipitation test (AGDT) using the agar and method described by Ok 0 Y e and U z 0 u k w u (1981).For detection of precipitins.the positive control was known IBD antiserum and negative control was normsl serum.In antigen detection, the positive control was a suspension of infected bursa while the negative control was normsl bursal suspension.

Reaulta
. Precipitation linea were obtained between the rat tissue suspension and known IBD virus anti,en within 36 hours in 6 samples.Other samples were ne,ative for both IBD vtral anti,en and precipitin.But the positive controls had positive results and the ne,ative controls were ne,ative.

Discuasion
The observations indicate that wild rats are susceptible to IBD virus Infection.The possibility of the infection producln, clinical si,ns and patholo,ical lesions as in sucklin, mice (C a m mar a t a et al. 1979) Is outside the scope of this paper.
The detection of IBD viral precipitins in tissue suspensions has been reported in chickens by Ide (1975), U 1 b ric hand Z u r e c k (1977) and a k 0 y e (1983).This method was used in this study because it was not possible to catch the rats alive.The method CaR also .beuseful in screenin, other wild mammalian and avian species for IBD virus infection.It is however possible that tissue suspensions may ,ive lower number of positive results than serum samples.Ed, a rand C h 0 (1976) mentioned that there was no convincin, evidence that the presence of rodents was related to the spread of IBD.But the results bf this investi,ation show that IBS virus can mUltiply in wild rats in sufficient quantities to induce the production of detectable precipitins.It is therefore possible that the rats can dischar,e the virus in their excrements like faeces and this may lead to spread of IBD amon, poultry farms.Ed, a r and C h 0 (1976) reported that the major means of spread of IBD virus to new areas was by movement of left-over finisher ration (diet) from hoppers on an lBO-farm to a susceptible flock on clean premises.This practice is not common in Ni,erian poultry husbandry but IBD has spread to all the 19 states of the country since it was first confirmed.