Comparative susceptibility of chickens, turkeys and ducks to infectious bursal disease virus using immunohistochemistry.

Twenty chicks, 12 turkey poults and 10 ducklings, all 5 weeks old were infected with 2 x 10(3.5) chick LD(50) IBD virus to determine the course of the virus in the 3 poultry species. Uninfected control birds were kept separately. Two infected and 2 control birds/species were euthanized at time intervals between 3 and 168 hours post infection (pi). Sections of thymus, bursa of Fabricius, spleen, liver, kidney, proventriculus and ceacal tonsil were stained for the detection of IBD virus antigen using immunoperoxidase technique. IBD virus antigen positive cells stained reddish-brown and the amount of such cells in tissue sections were noted and scored. Stained cells were present in all organs examined for up to 168 hours pi in the 3 poultry species except ceacal tonsils of ducks at 72 and 120 hours pi. Antigen score was highest in chickens and least in ducks as reflected by average of total scores/sampling time of 12, 10.8 and 8 in chickens, turkeys and ducks respectively. Total antigen score/sampling time in infected chickens peaked twice; 24/48 and 144 hours pi, whereas such bi-phasic peaks were absent in turkeys and ducks. Range of total antigen score at different sampling times was 7-17.5 in chickens, 10-13 in turkeys and 7-10 in ducks indicative of marked viral replication in chickens. Presence of IBD viral antigen in organs of all 3 poultry species is indicative of infections. The innate ability of turkeys and ducks to prevent appreciable replication of IBD virus after infection requires further investigation.

Prevalence of contagious bovine pleuropneumonia (CBPP) in northern Nigeria.

An abattoir study on the prevalence of contagious bovine pleuropneumonia (CBPP) in five cattle-producing states of Nigeria from 1988 to 1997 was carried out. A total of 1,936,015 slaughtered cattle was examined for characteristic CBPP lung lesions. The overall lesion-based prevalence of CBPP was 0.29% (95% CI 0.24, 0. 35). The prevalence varied significantly (P<0.05) by state but not across the years. A total of 279 CBPP outbreaks occurred and overall vaccination coverage was only 9.7%, both varied over the years and across the states. The reasons for inadequate vaccination coverage for CBPP as well as the need for re-establishment of a national CBPP control programme are suggested.

Dealing with animal disease emergencies in Africa: prevention and preparedness.

Emergency preparedness planning for animal diseases is a relatively new concept that is only now being applied in Africa. Information can be drawn from numerous recent disease epidemics involving rinderpest, contagious bovine pleuropneumonia (CBPP) and Rift Valley fever. These examples clearly demonstrate the shortcomings and value of effective early warning with ensured early reaction in the control of transboundary animal disease events. In concert, the Food and Agriculture Organization (FAO), through the Emergency Prevention-System for Transboundary Animal and Plant Pests and Diseases (EMPRES), and Organisation of African Unity/Inter-African Bureau for Animal Resources (OAU/IBAR), through the European Commission-funded Pan-African Rinderpest Campaign (PARC), have been actively promoting the concepts and application of emergency preparedness planning and should continue to do so under the proposed successor of PARC, namely: the Pan-African Programme for the Control of Epizootics (PACE). The potential partnership between the normative function of the FAO in developing and promoting emergency preparedness and the implementation of improved national and regional disease surveillance by PACE and other partners could witness the commencement of more progressive control of epidemic diseases in Africa and greater self-reliance by African countries in coping with transboundary animal disease emergencies.

Disease prevention and preparedness: the Food and Agriculture Organization Emergency Prevention System.

In 1994, the Food and Agriculture Organization undertook to revitalise its activities in the control of transboundary animal disease by establishing a new special programme known as the Emergency Prevention System (EMPRES) against transboundary animal and plant pests and diseases. The emphasis of the EMPRES livestock component is placed on pre-empting outbreaks and losses experienced by agriculture through the enhancement of local capacity to detect and react rapidly to plague events. EMPRES concentrates on the co-ordination of the Global Rinderpest Eradication Programme--a time-bound eradication programme--whilst addressing the progressive control of the most serious epidemic diseases within a broad framework of emergency preparedness. Programme activities are discussed in relation to early warning, early reaction, facilitating research and co-ordination. In addition to rinderpest, particular attention has been paid to contagious bovine pleuropneumonia, a re-emerging disease in Africa targeted for strategic attention, and foot and mouth disease, for which co-ordinated regional control in Latin America and South-East Asia has been initiated. Tactical responses to other disease emergencies such as African swine fever, classical swine fever (hog cholera), Rift Valley fever, peste des petits ruminants and lumpy skin disease are described.

Identification of a subpopulation of immune Nigerian adult volunteers by antibodies to the circumsporozoite protein of Plasmodium falciparum.

Collections of human sera from malaria-endemic areas would be valuable for identifying and characterizing antigens as malaria vaccine candidates if the contributing serum donors' ability to resist infection were fully characterized. We prepared such a serum collection from 26 apparently immune Nigerian adults who failed to develop patent parasitemia for at least 20 weeks following a documented increase in antibodies to the circumsporozoite protein (CSP) from Plasmodium falciparum. Volunteers were evaluated five times per week for malaria symptoms and bimonthly for parasites by examining thick blood smears. The incidence rate over 13 months for the cohort was 42% (47 malaria-confirmed volunteers) and the risk of infection was 1.3 infections/year. Responses to CSP did not correlate with protection. Because antibody responses to antigens other than CSP may be associated with protection, the sera from these immune individuals may be useful for identifying and characterizing other potential malaria vaccine candidates.

Identification of epitope expression on the internal proteins of rinderpest virus which is dependent upon virion maturation events.

Monoclonal antibodies (MAb) identified the existence of both maturation-dependent and maturation-independent epitopes on rinderpest virus antigens. The former were divided into (i) post-maturation antigenic determinants, which were dependent upon the maturation of viral antigen into complete virions; and (ii) pre-maturation antigenic determinants, which were only expressed on what appeared to be immature particles before 'budding' into the extracellular environment. Epitope expression could be related to the kinetics of virus production, with the 'post-maturation' sites requiring the production of mature/infectious virions, but the 'pre-maturation' sites being lost when mature virus was formed (these 'pre-maturation' determinants were strongly cell-associated). MAb against the different virion proteins of measles virus, when reacting with rinderpest virus did not demonstrate the same relationship to virion maturation as did the anti-rinderpest virus MAb: the anti-measles virus MAb detected maturation-independent epitopes. This work demonstrates the caution which should be taken when preparing antigens for diagnostic and epidemiological purposes, especially when MAb are being used to identify antigenic differences between isolates, and/or to compare antigenically isolates with vaccine viruses.

Rapid isolation of monoclonal hybridoma cultures by a 'fusion-cloning' method: the requirement for aminopterin.

Hybridomas were generated by fusing the Balb/c SP2/0 myeloma-like cell line with either: (i) splenocytes from Balb/c mice immunized with foot-and-mouth disease virus (FMDV), rinderpest virus (RPV), peste des petits ruminants virus (PPRV), African swine fever virus (ASFV) or pig thymocytes; or (ii) lymph node cells from cattle immunized with FMDV. If the fusion mixtures were plated in cloning medium of methyl cellulose and HAT medium, small hybridoma colonies developed which rarely survived. Fusion mixtures were then plated in liquid HT medium on to 3T3/A31 feeder layers in 75 cm2 flasks, incubated at 37 degrees C for 24 h before adding aminopterin, and incubated for a further 2 to 4 days before cloning in methyl cellulose/HT medium. Without the aminopterin in the cloning medium, colonies of hybridomas, which could be cultured, developed from the majority of fusions. These colonies were isolated in HT medium over feeder layers and given two subcultures in HAT medium as a precaution against any reversion to aminopterin sensitivity during the cloning. No evidence of such reversions were seen, and recloning results suggested that the initial cloning was highly efficient at generating monoclonal cultures.

Identification of epitope(s) on the internal virion proteins of rinderpest virus which are absent from peste des petits ruminants virus.

Monoclonal antibodies (MAb) raised against the RBOK vaccine strain of rinderpest virus were characterized by radio-immunoprecipitation (RIPA) and in the indirect ELISA using measles (MV), distemper (CDV), rinderpest (RPV) and peste des petits ruminants viruses (PPRV). Those found to be specific for the matrix (M) protein and the nucleocapsid (N) protein could be classified into different groups on the basis of the anti-morbillivirus MAb classification scheme; a number of these MAb showed a selective recognition of RPV, measles virus and distemper virus, or of different isolates of rinderpest virus, demonstrating that greater inter-isolate variation occurs than was apparent from analyses using polyclonal antisera. One group of anti-F protein MAb (group F1) reacted with all isolates of both RPV and PPRV. A second group of anti-N protein MAb (group N1/A) reacted with all RPV isolates, but not with the PPRV isolates. Furthermore, these group N1/A antibodies reacted strongly with RPV isolates which were upon original isolation of high pathogenicity, but had a weaker reaction against the isolates of this virus which were of low pathogenicity. Thus, MAb against RPV, in particular those against the N protein offered a potential superior to that of molecular analyses for "isolate fingerprinting", the differentiation of RPV from PPRV and the discrimination between rinderpest viruses which had been, upon isolation, of either high or low pathogenicity.

The production of peste des petits ruminants hyperimmune sera in rabbits and their application in virus diagnosis.

Hyperimmune sera were produced by serial inoculation of rabbits with Vero cell-adapted, sucrose gradient-purified Nigerian peste des petits ruminants virus (PPRV) isolate. Two antisera produced, neutralized the homologous PPRV but not the heterologous rinderpest Kabette "O" virus. The antisera gave strong precipitin lines with purified PPRV antigens and were used to detect PPRV and rinderpest virus antigens from ante-mortem secretions and post-mortem tissue homogenates from PPR and rinderpest virus infected goats and cattle by the agar gel precipitation tests (AGPT). The hyperimmune sera gave good titration curves with both purified Nigerian goat and the United Arab Emirate wildlife PPRV isolates in the indirect enzyme linked immunosorbent assay (ELISA). Results of indirect ELISA showed that although there were some cross reactions with the rinderpest, canine-distemper and measles viruses, at 1:100 dilution, the antisera would give a positive signal with only the homologous PPR virus.

Dot enzyme immunoassay for visual detection of peste-des-petits-ruminants virus antigen from infected caprine tissues.

An enzyme-linked immunosorbent microassay using nitrocellulose paper as the solid-phase support was developed for the detection of peste-des-petits-ruminants virus antigens in infected caprine tissue homogenates. Dots of tissue homogenates were applied to nitrocellulose papers, and any unreacted sites were blocked with 5% skim milk powder in triethanolamine-buffered saline. After incubation of the papers in tissue culture supernatant monoclonal antibody against the peste-des-petits-ruminants virus, the antigen-antibody reaction was detected with peroxidase-conjugated anti-mouse immunoglobulin G and the enzyme substrate 4-chloro-1-naphthol. Positive results were visualized as blue dots. Results of the dot enzyme immunoassay compared favorably with those of the standard enzyme-linked immunosorbent assay. Incorporation of Nonidet P-40 in the washing solution did not improve the sensitivity of the dot enzyme immunoassay, and pretreatment of homogenates with Nonidet P-40 before application to the nitrocellulose paper inhibited the binding of the antigen to the paper and reduced the intensity of the color development.

An outbreak of peste des petits ruminants in a zoological collection.

Peste des petits ruminants virus was suspected to be the cause of a disease outbreak in a zoological collection at Al Ain in the Arabian Gulf. Clinically the outbreak affected gazelles (Gazellinae), ibex and sheep (Caprinae) and gemsbok (Hippotraginae); subclinical involvement of Nilgai (Tragelaphinae) was suspected. A morbillivirus was isolated and using monoclonal antibodies and biological tests in cattle, sheep and goats the virus of peste des petits ruminants was identified.

The detection of peste des petits ruminants (PPR) virus antigen by agar gel precipitation test and counter-immunoelectrophoresis.

The detectability of peste des petits ruminants (PPR) viral antigen in both ante-mortem secretions and necropsy samples from experimentally infected goats was investigated by both the agar gel precipitation test (AGPT) and counter-immunoelectrophoresis (CIE). Viral antigen was detected from 42.6% of the samples tested by the AGPT and 80.3% by CIE. The detection of viral antigen in a high proportion of the ocular and nasal secretions as well as the faeces and buccal scrapings, particularly from those collected within seven days of the onset of fever, by both techniques, would seem to obviate the need for lymph node biopsies or post-mortem samples in order to make a diagnosis of PPRV infection.

Serological studies with peste des petits ruminants and rinderpest viruses in Nigeria.

One hundred and ninety-five goat and 67 sheep sera collected from various parts of southern Nigeria were screened for neutralising antibodies to both the peste des petits ruminants (PPR) and rinderpest viruses. Neutralising antibodies against both viruses were found in the sheep and goat sera examined. Parallel titration of samples which neutralised both viruses indicated a primary infection with the PPR virus (PPRV). However, some samples which failed to neutralise PPRV neutralised the rinderpest virus (RV) indicating RV activity in sheep and goats in Nigeria. These findings are discussed in relation to the diagnosis of PPRV infection and the recent reappearance of bovine rinderpest in Nigeria.

Serological survey of adenovirus antibodies in domestic animals in Nigeria.

Serum samples collected from 1,197 goats, 586 sheep, 254, cattle, 55 dogs and 44 horses were examined for antibodies to adenovirus by the agar-gel precipitation test. Results show that 17.7% of the goats, 18.4% of the sheep, 4.3% of the cattle, and 4.5% of the horses had precipitating antibodies. None of the dog sera examined was positive. The results seem to indicate a moderate level of previous exposure to adenovirus infection especially among goats and sheep in Nigeria.

Response of Nigerian zebu cattle to zeranol implants.

The effect of Zeranol, an anabolic agent, on the weight gains of Nigerian zebu fattening bulls was investigated over a period of 16 weeks. Implanted Sokoto Gudali and White Fulani bulls showed average daily weight gains of 0.5 and 0.49 kg respectively as compared to 0.47 and 0.41 kg by non-implanted counterparts. The anabolic effect of Zeranol was evident up to 8 to 9 weeks after implantation, after which there was no significant difference in weight gains of implanted and control animals.