Search

Information on veterinary public health organisation and activities was obtained from government sources in countries located in the Western Pacific region. This region has a wide range of geographical features, population densities, farming practices, social structures and disease prevalences. In spite of this variation, there is common agreement on the importance of veterinary public health both for the provision of safe food and for the control of zoonotic diseases. Not all countries, however, are able to put all the resources they would wish into these activities; financial, social and personnel constraints are recognised.

An immunocytochemical technique utilizing an avidin-biotin peroxidase complex was developed to detect viral antigens in various tissues following oral administration of a locally isolated serotype 8 avian adenovirus (AAV) in specific pathogen-free (SPF) chickens. A strong color reaction was obtained with tissues from infected birds that contained a minimal amount of AAV antigens as determined by an indirect enzyme-linked immunosorbent assay. No reaction was detected in sections of tissues obtained from SPF chickens, and the reactivity with infected tissues could be removed by prior absorption of the primary antibody with purified AAV. A group-specific antigen common to the 12 serotypes of AAV was demonstrated by this technique. Because of the high sensitivity and broad-spectrum reactivity, this technique could be useful for studying the pathogenesis and laboratory diagnosis of inclusion body hepatitis caused by several serotypes of AAV.

Sera collected from the Australian brush-tailed possum Trichosurus vulpecula in New Zealand in 1975 and 1989 were tested for the presence of antibodies to adenovirus. Of the 231 sera tested in an agar gel diffusion test, eight (3.5%) had precipitating antibodies to the group specific antigen of mammalian adenoviruses. Available data allowed 99/231 sera to be classified as being obtained from either adult (total 62) or sexually immature (total 37) possums. From the adult animals, 4/62 (6.5%) sera were positive, while no reactive sera were detected among the 37 immature animals. The results provide evidence that natural infection by an adenovirus occurs in possums in New Zealand. Further work needs to be carried out to isolate this adenovirus to enable detailed serological and epidemiological studies to be performed. A species-specific possum adenovirus could have potential in the biological control of this species.

Using an indirect enzyme-linked immunsorbent assay, avian adenoviral antigens were detected in the yolk and albumen of eggs derived from broiler breeder chickens which were known to be infected with a strain of virus capable of causing inclusion body hepatitis. Viral antigens were detected in egg yolk (16/60) more frequently than in the albumen (5/60). Direct detection of viral antigens in eggs strongly supports the hypothesis that transovarian transmission of inclusion body hepatitis virus occurs if infection is present in breeder flocks.

Unpurified DNA derived from cultures of equine fetal kidney cells infected with either equine herpesvirus type 1 or equine herpesvirus type 4 was amplified by the polymerase chain reaction using one pair of oligonucleotide primers. Restriction endonuclease digestion of the amplified segments with PvuII, followed by electrophoresis, revealed restriction fragment length polymorphisms which enabled the two virus types to be differentiated.

The pathogenesis of inclusion body hepatitis was studied following the oral administration of a serotype 8 strain of avian adenovirus into 2-day-old specific pathogen free chickens. Viral antigens were detected in tissues at various times post inoculation (pi) by enzyme-linked immunosorbent assay and by immunocytochemistry. Viral antigens were detected in intestinal epithelium from 12h to 13 days pi and in the plasma fraction of blood by 24 h pi. A biphasic, cell-free viremia with peaks at 2 and 7 days pi was recorded. Antigens were first detected in the liver from 2 days and reached peak levels at 6 days pi. The second peak of viral antigens in blood plasma was probably due to release of virus from damaged hepatic cells. Initially, viral antigens in the liver were restricted to cells lining the sinusoids but increasing involvement of hepatocytes occurred with time. Small amounts of viral antigens were detected in other tissues. Following the appearance of neutralizing antibodies in serum from 7 days pi, the levels of viral antigens in all tissues decreased and were undetectable by 15 days pi. This viral hepatitis of chickens is possibly a useful model for other viral infections where a cell-free viremic phase is important for spread of virus from primary sites to target organs, such as the liver.

Conventionally raised chickens were inoculated with a local isolate of serotype 8 of avian adenovirus by an oral or intraperitoneal route, or were exposed to the infection by contact. Fatal hepatitis, resembling inclusion body hepatitis, occurred in 30% and 45% of the birds inoculated by the oral and intraperitoneal routes respectively, and severe growth depression was recorded in survivors and in birds in contact. Birds which had maternally derived virus neutralising antibody titres of 64 or greater at the time of viral exposure did not succumb to fatal infection, but their growth rates were significantly depressed.

An enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of antirotaviral antibody in sera and faeces from pigs and used to study the dynamics of antirotaviral antibody responses in three cohorts of pigs. Piglets acquired antirotaviral antibody by sucking their dams soon after birth. Antirotaviral antibodies of IgA and IgG classes were detected in both colostrum and milk of all sows tested but IgM class antibodies were not. The antibody levels in colostrum were eight to 32 times higher than those in milk which was collected 18 days post partum. The levels of antibody in piglets' sera were comparable to those in colostrum but declined quickly to low levels by one month old. Maternal antibody was also detected in the faeces of piglets up to 18 days old. Natural rotavirus infection occurred in each of these cohorts when the geometric mean ELISA titres of maternal antibody in their sera declined to 1/1600 (by days 21, 25 and 30 for cohorts 1, 2 and 3, respectively). However, a positive correlation was not obtained between the levels of antirotaviral antibody and protection in individual litters within each of the cohort groups. In each of the cohorts, rotavirus infection usually occurred in one or two piglets first and then spread to other piglets in the same cohort. It is therefore suggested that maternally derived antibody is protective against rotavirus infection in piglets only for the first one or two weeks. Following natural infection with rotavirus, increases in serum antibodies were detected in two of the three cohorts by 20 to 30 days after the average time of onset of faecal shedding of virus.(ABSTRACT TRUNCATED AT 250 WORDS)

An indirect enzyme-linked immunosorbent assay (ELISA) was developed to detect and quantify avian adenovirus (AAV) in various chicken tissues, including blood. A positive ELISA absorbance value was obtained with suspensions of infected liver tissue that contained less than 100 mean tissue-culture infective doses per gram. A positive correlation was observed between the absorbance values and titer of infectious virus in infected liver tissue. A group-specific antigen common to the 12 serotypes of AAV tested was demonstrated by this ELISA. Because of the high sensitivity and broad-spectrum reactivity, this ELISA could be useful for the study of AAV pathogenesis, for laboratory diagnosis of inclusion body hepatitis irrespective of the serotype of AAV involved, and for screening commercial and specific-pathogen-free flocks for the presence of AAV.

The DNAs of a number of herpesviruses from Australian marsupials have been analyzed using restriction endonucleases, dot-blot hybridizations, and analytical ultracentrifugation in CsCl. The data clearly show the presence of 2 distinct viruses, designated macropodid herpesviruses 1 and 2.

A total of 1,355 random samples taken from bovine serums submitted for brucellosis testing in Victoria were submitted to the microscopic agglutination test for the presence of antibody to 12 serovars of Leptospira interrogans. The most common reaction obtained was to serovar hardjo, although the percentage of reactors varied from 24.8% in the metropolitan area to 56.3% in north-eastern Victoria (mean 40.6%). A total of 86.3% of farms from which 3 or more samples were taken had at least one reactor to serovar hardjo. The prevalence of antibody to other serovars was tarassovi (7.8% of reactors), ballum (3.7%), pomona (2.4%), autumnalis (1.8%) and bataviae (1.2%). Reactions to other serovars were observed in serums of less than 1% of cattle tested; serums from 50.8% of cattle did not react to any antigen.

Virus-neutralizing antibody does not protect animals challenged with the herpesvirus of bovine malignant catarrh; therefore, other parameters of the immune response were investigated. In vitro transformation of peripheral blood lymphocytes with mitogens and specific antigens was monitored throughout the course of disease in lethally infected New Zealand white rabbits. The whole-blood culture method was used. Transformation with mitogens was normal throughout the incubation period but fell precipitously from the day of disease onset until death. Specific stimulation with viral antigens was not detected at any time following challenge. Purified and washed lymphocytes, however, reesponded normally to mitogens and were transformed in the presence of viral antigens. Acute-phase serum from rabbits inhibited transformation of normal rabbit lymphocytes, but this inhibition was reversible by washing. It is proposed that the development of a serum suppressive factor(s) is important in the determination of whether an animal is capable of controlling infection with this virus.

The long term efficacy of a commercially prepared bivalent vaccine against Leptospira interrogans serovar hardjo and L. interrogans serovar pomona was evaluated in a group of 82 dairy heifers exposed to natural challenge with L. interrogans serovar hardjo for up to 55 weeks after calfhood vaccination. Nineteen heifers were vaccinated twice with a one-month interval, at calfhood (9 to 10 months). A further 18 heifers received a similar calfhood vaccination regimen plus a third injection at adulthood (22 to 23 months), while 19 heifers were vaccinated twice at adulthood only and finally 22 heifers were used as unvaccinated controls. At 55 weeks after calfhood vaccination and prior to adulthood vaccination, only 2.7% of the vaccinated heifers were found to have leptospiruria compared with 58.5% of the unvaccinated heifers (p less than 0.0001). Microscopic agglutination (MA) titres at the same time in the unvaccinated heifers ranged from 32 to 4096 while those vaccinated at calfhood ranged from 32 to 64. Adult vaccination of infected animals did not significantly reduce leptospiruria . Prior to adulthood vaccination, 9 of 19 heifers had leptospiruria , in comparison to 4 of 15 after adulthood vaccination. At the same sampling periods 15 of 22 controls had leptospiruria in comparison to 4 of 9 subsequently tested.

The DNAs of virulent and avirulent strains of infectious laryngotracheitis virus (ILTV) showed greater than 96% homology by reciprocal DNA:DNA hybridization. Nevertheless, by use of selected restricted DNA fragments, it was possible to differentiate strains according to pathotype more readily than by the more laborious restriction enzyme analysis. Restricted DNA fragments were successfully cloned into Escherichia coli HB101 cells and could be used not only for pathotyping ILTV strains but also for their differentiation from other avian viruses.

A microculture technique was developed for the in vitro blastogenesis of feline lymphocytes. Blastogenesis of ficoll-diatriazoate gradient separated mononuclear cell, washed blood and whole blood were compared. In general the whole blood cultures yielded higher stimulation indices (SI) than the washed blood or separated mononuclear cell cultures. The effect of several variables on the stimulation of lymphocyte cultures was examined. A cell concentration of 3 x 10(5) cells/well and a 1:20 dilution of washed and unwashed whole blood gave optimal stimulation with concanavalin A (Con A). Phytohaemagglutinin-P (PHA-P) did not give significant levels of stimulation. Inactivated fetal calf serum (FCS) at levels of 2.5% (for washed blood) and 5% (for separated mononuclear cell and whole blood) gave highest SI. Supplementation with FCS was preferable to autologous, homologous or horse sera for all cultures. Optimal SI was obtained in all cultures incubated for 3 days and labelled with 1 microCi tritiated thymidine (3H-TdR) for the last 16 hours. The highest SI were in the range of 70 to 105 (18,764 to 42,681 counts per minute (CPM) for separated mononuclear cell culture, 100 to 165 (28,403 to 45,334 CPM) for washed blood culture and 105 to 186 (41,076 to 69,999 CPM) for whole blood culture.

To determine the pathogenic potential of the vesiculoviruses Isfahan and Chandipura for domestic animals, two ponies, two steers, three sheep, three goats and three pigs were inoculated with each virus intradermally in the tongue or, in the case of the pigs, in the snout, heel and coronary band. The ponies were also inoculated intradermally in the right commissure of the mouth. Animals inoculated with each virus were housed in one room and allowed to mingle freely with an equal number of uninoculated contact animals of each species. Clinical signs of infection, consisting of ulcers at the inoculation sites, were observed in the Chandipura study in two inoculated ponies, one inoculated steer and one inoculated goat. No elevated temperature was observed. Virus was isolated from the ulcerated tongue tissue, but not from serial blood samples, oesophageal-pharyngeal mucus samples, or from the tissues which were collected at necropsy. Precipitating antibody was not detected by the immunoelectroosmophoresis (IEOP) test in any of the pre- or post-serum samples except from two inoculated sheep at 29 days post-inoculation (D.P.I.). Low levels of neutralizing activity were detected in pre-inoculation serum from all steers, pigs, contact sheep, and one contact goat. By 15 D.P.I. all inoculated animals and contact ponies and steers exhibited increased neutralizing antibody titres. In studies with the Isfahan virus, lesions developed only at the inoculation sites in the two ponies, and the virus was isolated. No virus was isolated from any blood, oesophageal-pharyngeal mucus samples or tissues collected at necropsy. All pre-inoculation sera were negative for neutralizing and precipitating antibodies. By 14 D.P.I. all inoculated animals exhibited neutralizing antibody, while all the contacts remained negative. The IEOP test remained negative for all animals throughout the experiment. A sub-passage of a suspension of Isfahan-infected tongue tissue injected into ponies and steers also yielded only firm swellings of lesser extent than the original reaction at the inoculation sites. With both viruses, lethal infections were produced by intracranial or intraperitoneal inoculation of day-old mice and hamsters, and by allantoic inoculation of embryonating chicken eggs. Adult mice, hamsters, guinea-pigs and rabbits produced serum antibodies but lacked clinical signs.

A severely dehydrated foal with a history of acute diarrhoea was presented to Massey University for treatment. Rotavirus was demonstrated in the faeces by electron microscopy. The failure to detect other pathogens suggested that rotavirus was the primary aetiological agent. Successful treatment of this case is described and the principles of treatment for diarrhoea, particularly fluid therapy, are reviewed. Antibodies to rotavirus were detected in the sera of nine mares and their foals on the stud that referred the case, indicating that rotaviral infection was probably endemic.

Twenty-two ponies were examined for serum-neutralizing (SN) antibody to equine herpesvirus type 1 and for in vitro lymphocyte transformation in the presence of viral antigen. Six ponies had undetectable levels of neutralizing antibody (titer less than 1:2) and had lymphocytes which did not respond in culture with viral antigen (stimulation index less than 2.0). Four ponies which had SN antibody to equine herpesvirus type 1 did not manifest lymphocyte transformation in vitro. The 12 remaining seropositive ponies had lymphocyte transformation with viral antigen in vitro (stimulation indexes from 2.0 to 23.5). Lymphocyte transformation was specifically suppressed when cells were grown in medium containing autologous serum. The temporal development of in vitro lymphocyte responsiveness and SN antibody in 3 specific-pathogenfree ponies after experimentally induced infection with equine herpesvirus type 1 is described.

This study was conducted to develop a rapid test to detect type specific antibodies to various strains of vesicular stomatitis virus. Glycoprotein was extracted from purified vesicular stomatitis virus-Indiana 3 and used as antigen in an immunoelectroosmophoresis test (counter immunoelectrophoresis) to test reactivity with homologous hyperimmune serum and antisera to vesicular stomatitis virus-New Jersey, Indiana 1 and Indiana 2. A reaction was only detected with the homologous antiserum. A simpler preparation of antigen, a detergent extract of infected cells was also evaluated and shown to have less specificity in reactions with hyperimmune sera. This infected cell extract was, however, useful in detecting homologous antibodies in convalescent sera (natural vesicular stomatitis virus-New Jersey infection) and no reactions were detected with infected cell extracts of vesicular stomatitis virus-Indiana 1, 2 and 3.

The immune response in horses following experimental infection with equine herpesvirus type 1 (EHV-1) was assessed by measuring cytotoxicity for EHV-1-infected target cells. A technique was developed, using [125I]5-iodo-2'-deoxyuridine ([125I]IUDR)-labeled equine fetal kidney cells infected with EHV-1 as the target cells. It was shown that peripheral blood leukocytes from a recovered horse were capable of lysing target cells, as measured by the loss of radio-active label. Following the experimental infection of specific-pathogen-free ponies with EHV-1, cytotoxicity was obtained with fresh autologous serum, peripheral blood leukocytes in autologous serum, and washed peripheral blood leukocytes. Cytotoxicity of the serum and peripheral blood leukocytes was detected as early as one day after infection. It is suggested that cytotoxic antibodies or cells could play an important part in restricting virus spread after infection of the horse with EHV-1.

The efficacy of a vaccine against Leptospira interrogans serovar pomona and Leptospira interrogans serovar hardjo was evaluated in a group of dairy heifers that were serologically negative at the time of vaccination and later subjected to natural challenge with L. interogans serovar hardjo. Thirty-nine heifers were vaccinated twice, at a one-month interval, with a commercially prepared bivalent vaccine, while 43 unvaccinated heifers were used as controls. After vaccination, microscopic agglutination (MA) titres of serums to L. interrogans serovar hardjo ranged from 32 to 512, and those to L. interrogans serovar pomona ranged from 32 to 2048. Titres resulting from vaccination were short-lived and after the first vaccination the serums of 95% of vaccinated heifers did not react in the MA test by 24 weeks. The first indication of infection in the heifers was noted at week 6, and by week 16, elevated MA titres (greater than or equal to 128) to L. interrogans serovar hardjo had occurred in 62% of unvaccinated heifers and had increased to 85% by week 24. At week 18, 18% of the vaccinated heifers and 56% of the unvaccinated heifers had leptospiruria (p less than 0.01); after 22 weeks, 13% of the vaccinated heifers and 58% of the unvaccinated heifers showed evidence of leptospiruria (p less than 0.01).

Between May, 1979, and May, 1981, leptospirosis was diagnosed, on the basis of serological and culture findings, in specimens from 208 of 2516 patients with symptoms which suggested leptospirosis or other zoonoses. The most common serological reactions were with serovars hardjo (69%), pomona (29%) and tarassovi (2%). There was a clear association between infection and occupation in 101 farmers, 44 meat workers and 11 meat inspectors. It would seem prudent to consider leptospirosis in the differential diagnosis of pyrexia in patients who have occupational contact with animals, and to institute appropriate serological and culture examinations.

The immunological and virological status of 3 foals in respect of equine herpesviruses (EHV) was established and the foals were sequentially infected with EHV2, EHV3 and EHV1. Following experimental infection with EHV2, no clinical signs of disease were observed in any foal. The inoculation of EHV3 into the genital tract resulted in lesions of the mucous membrane and perineal skin that were considered typical of equine coital exanthema. Following intransal inoculation of EHV3 extensive ulceration and pustule formation on the nasal mucosa was observed by day 5 accompanied at day 7 by a profuse, mucopurulent nasal discharge; on day 8 pustular lesions of the skin about the external nares appeared. Signs of disease after inoculation with EHV1 were milder than expected in 2 of the 3 foals. The possibility that recent, prior infection with EHV2 and/or 3 may protect against EHV1 was considered.

Immune responses to Rhodococcus equi were assayed in mares and foals on 7 studs in south-eastern Australia using skin test reactivity to the intradermal injection of culture filtrate and an indirect fluorescent antibody test. The prevalence of positive skin-test reactions did not differ between studs with a history of R. equi disease and those without but there were more mares with high antibody titres on studs with a disease history. A leucocyte extract prepared from mares that were skin-test positive was evaluated for its ability to protect foals exposed to experimental or natural challenge: 2 foals receiving leucocyte extract became skin-test positive and had resolving lesions present at post-mortem examination. All foals challenged experimentally developed serum antibody but only in those that became skin-test positive were the lesions resolving. In a field trial of leucocyte extract, using 450 foals over 2 foaling seasons, no significant difference was detected in morbidity or mortality rates between treatment and control groups. It is suggested that, since R. equi is so ubiquitous and most horses show immunological evidence of exposure, the development of clinical disease may be related to individual inability to cope with this organism. This may be due to inherited immunological unresponsiveness or to environmental factors which increase the challenge or decrease resistance.

Strains of infectious laryngotracheitis virus (ILTV) were examined using an indirect immunofluorescent test (IIF) and with restriction endonucleases for detecting intratypic differences. Electrophoretic analysis of ILTV DNA fragments cleaved with restriction endonuclease Hind 111 clearly distinguished between strains. The IIF test did not discriminate between strains. A molecular weight estimate of ILTV DNA was made by summation of restriction endonuclease fragments cleaved with BamH1 (102.1 X 10(6)) and Hind111 (97.35 X 10(6)). Differences between the estimates may indicate the presence of submolar fragments.

Eight bulls which gave positive reactions in the complement fixation test for Johne's disease were identified in a group of 29 bulls which had previously given only negative reactions at repeated annual tests. One reacting bull was confirmed to be infected with Mycobacterium paratuberculosis at autopsy, but another reactor which was slaughtered had no visible lesions and mycobacteria were not recovered in culture. Faecal samples from seven further bulls (six reactors and one non-reactor) yielded mycobacteria which were not dependent on mycobactin for growth. When one of these strains was injected into two calves they developed positive reactions in the complement fixation test for Johne's disease and to intradermal skin testing with purified protein derivatives of M avium, M paratuberculosis and M bovis. The strains did not satisfy the exact requirements for classification into any recognised mycobacterial species.

Anti-leptospiral agglutinins were found in the serum from 18 (7 species) of 419 (25 species) animals sampled from various areas of southeastern Australia. Positive serologic reactions were observed in 5 of 25 (20%) brush-tailed possum (Trichosurus vulpecula), 1 of 26 (3.8%) tammar wallaby (Macropus eugenii), 2 of 12 (16.7%) swamp wallaby (Wallabia bicolor), 1 of 3 (33.3%) koala (Phascolarctos cinereus), 3 of 41 (7.3%) common wombat (Vombatus ursinus), 2 of 100 (2%) bush rat (Rattus fuscipes) and 4 of 12 (25%) rusa deer (Cervus timorensis). The majority (55.5%) of serologic reactions were to serovar hardjo. No serologic reactions were observed in samples from echidna (Tachyglossus aculeatus), brown antechinus (Antechinus stuartii), swainson's antechinus (Antechinus swaisonsii), long-nosed bandicoot (Perameles nasuta), brown bandicoot(Isoodon obesulus), common ringtail (Pseudocheirus peregrinus), greater glider (Schoinobates volans), eastern grey kangaroo (Macropus giganteus), red-necked wallaby (Macropus rufogriseus), rabbit (Oryctolagus cuniculus), water rat (Hydromys chrysogaster), black rat (Rattus rattus), eastern swamp rat (Rattus lutreolus), broad-toothed rat (Mastacomys fuscus), fox (Vulpes vulpes), sambar deer (Cervus unicolor), hog deer (Axis porcinus) and fallow deer (Dama dama).

Infectious laryngotracheitis virus (ILTV) DNA was prepared using sodium iodide equilibrium centrifugation, preferential phosphorus-32 labelling and extraction with the detergent Triton X 100. The Triton X 100 procedure was found to be the preferred method for preparing DNA for analytical purposes. A method for ILTV titre enhancement is described.

To determine the pathogenic potential of the vesiculovirus Piry for domestic animals, two ponies, two steers, three sheep, three goats and three pigs were inoculated intradermally in the tongue or, in the case of the pigs, in the snout, heel and coronary band. Inoculated animals were housed in one room and allowed to mingle freely with an equal number of uninoculated contact animals of each species. Clinical signs of infection, consisting of elevated temperature and ulcers at the inoculation sites, were only observed in the ponies, but all inoculated animals developed specific antibody following inoculation. In addition, one of the contact sheep had neutralizing antibody to Piry at 7 and 29 days post inoculation suggesting a contact infection. Virus was not demonstrated in tissues, other than tongue, of any animal. The failure of Piry virus to produce lesions in steers, sheep, goats and pigs and only limited ulcerations in ponies suggests that this virus is not similar pathogenically to New Jersey and Indiana strains of vesiculoviruses which produce classical vesicular stomatitis. Lethal infections were produced by inoculation into suckling mice and hamsters, adult hamsters and embryonating chicken eggs. Further, lethal infections followed contact of adult female hamsters with their inoculated litters.

The accuracy with which the purified lymphocyte and whole blood modifications of the lymphocyte stimulation test were able to detect animals with clinical Johne's disease was compared with that of the complement fixation test and microscopic faecal examination. Confirmatory diagnosis of Johne's disease was based upon histopathological examination of intestinal tissue. False positive results were obtained only with the complement fixation test. The only test not giving rise to false negative results was the purified lymphocyte modification of the lymphocyte stimulation test using johnin at 20 micrograms/ml and avian tuberculin at 20 micrograms/ml or 2 micrograms/ml. The whole blood technique was less accurate than the purified lymphocyte technique for the in vitro detection of cell-mediated immune responses to antigens. The purified lymphocyte technique appears to have potential as an diagnostic test for Johne's disease in cattle and merits further evaluation.

Two cases of leptospirosis due to infection with a member of the Hebdomadis serogroup are described in farm workers on a Victorian dairy farm. The source of infection appeared to be the milking herd which had elevated serum antibody titres against a member of the Hebdomadis serogroup. Agglutinin-absorption testing of one patient's serum indicated that the infecting serovar was hardjo. A survey of 1,144 cattle entering abattoirs throughout the State indicated that 44.3% of these animals showed serological evidence of past or present infection with leptospira of the Hebdomadis serogroup and the potential risk for people with occupational contact with cattle is emphasised. The importance of considering leptospirosis in the differential diagnosis of all patients with influenza-like symptoms or pyrexia of unknown origin and having occupational contact with animals, especially cattle, is discussed.

Polyacrylamide gel electrophoresis (PAGE) and enzyme-linked immunosorbent assay (ELISA) were employed to investigate the epidemiology of typical and atypical rotavirus infections in five piggeries. Of 152 faecal samples examined, 46 (30 per cent) were positive by ELISA for group A rotavirus. Rotaviruses with electrophoretic patterns resembling groups A, B and C were detected. At least two and up to five different rotavirus electrophoretypes (typical and/or atypical) were detected in each of the five piggeries. Out of 152 faecal samples examined, 28 (18 per cent) contained rotaviruses with group A electrophoretypes, 9 (6 per cent) with group C but only 1 with Group B. Six samples contained both group A and group C rotaviruses. No common electrophoretypes of group A or C rotaviruses were detected in these five piggeries. The PAGE technique was also used to analyze group A rotavirus isolated sequentially from another piggery over a three year period. A single electrophoretype was found during the first two years, but in the third year a different electrophoretype was detected.

A reovirus was isolated from a flock of 12,000 broiler chickens which experienced a total mortality of 6.3% up to 35 days. The reovirus produced large syncytia in primary chicken kidney cell cultures with eosinophilic intracytoplasmic inclusion body formation. Infected cells reacted with fluorescein conjugated specific anti-reovirus serum. Negatively strained virions had a double shelled appearance with overall diameter of 65 to 70 nm. The nucleic acid had ten discrete segments with electrophoretic mobilities as would be expected for a reovirus.

The distribution of iron and mycobacteria was examined in the intestinal tract of ruminants with naturally-occurring M. paratuberculosis infection and compared with mycobacterial infections in several species. This distribution was compared with that of iron in chronic lesions caused by other microbial or parasitic agents. In the clinical form of paratuberculosis in cattle, sheep and goats there was marked lymphangiectasis and a high proportion of the granulomatous lesions contained siderotic macrophages with a high mycobacterial content. In cattle with preclinical lesions of granulomatous enteropathy, the greatest number of acid-fast organisms was present in siderotic, non-differentiated, ileo-caecal macrophages; concurrent mast cell-associated allergic enteropathy was also apparent in the duodenum, proximal and mid-ileum of most animals. In paratuberculosis-affected herds, a high proportion of non-productive cows were without classical granulomatous change but had cultural or immunological evidence of M. paratuberculosis infection and similar allergic catarrhal enteropathy of the upper intestinal tract. Interstitial haemorrhage of the ileocaecal valve, with the accumulation of haemosiderin and ferritin in undifferentiated macrophages was observed in some of these cattle and also in others with experimentally-induced copper deficiency and acute ostertagiasis. Colonisation of the ileo-caecal or caecal glandular crypts by large, apparently saprophytic acid-fast organisms indicated regional tolerance to such organisms in all cattle. In other mycobacterioses such as bovine or avian tuberculosis, undifferentiated, siderotic macrophages containing mycobacteria were also seen in early granulomas, but epithelioid and giant cell differentiation invariably led to the disappearance of intracellular iron and a reduction in mycobacterial numbers. In possums in which epithelioid and giant cells did not occur in response to M. bovis infection, siderosis persisted in many macrophages and overwhelming mycobacterial multiplication occurred. These studies indicate that, in most infections with mycobacteria, differentiation of macrophages radically reverses their iron acquisitive properties, creating an intracellular environment unsuitable for mycobacterial multiplication. It seems likely that allergically mediated microvascular haemorrhage, local tolerance of commensal mycobacteria and attenuation of the macrophage siderosis reversal mechanism provide unique conditions for early, uninhibited, intracellular multiplication of M. paratuberculosis in the ileo-caecal valve of certain mature ruminants.

An antiserum to a recent field isolate of infectious laryngotracheitis virus was conjugated with fluorescein isothiocyanate and used to detect viral antigen to infected chorioallantoic membranes and trachael epithelium by the direct fluorescent antibody technique. In experimentally infected birds, viral antigen was detected with the fluorescent antibody technique from 2 to 14 days post-inoculation but histological evidence of tracheitis was only observed from day three to day ten. The fluorescent antibody test detected 22 of 23 histologically confirmed cases of ILT and was more accurate than virus isolation when used in the diagnosis of respiratory disease from field outbreaks. It was concluded that the speed, accuracy and sensitivity of the fluorescent antibody technique make it a useful tool in the diagnosis of infectious laryngotracheitis.

The glycoproteins prepared from 7 Vesiculoviruses were differentiated by their electrophoretic mobilities in polyacrylamide gels and by reactions with anti-viral and anti-glycoprotein sera.