Journal of Hygiene最新文献

The brucellin skin test and the lymphocyte transformation test were compared in heifers infected with virulent Brucella abortus strain 544, heifers vaccinated against brucellosis and unexposed cattle. Results of the in vitro lymphocyte transformation test were consistently positive for all 9 Brucella-infected heifers while the skin test was consistently positive for 6 of the 9 heifers. In 7 heifers repeatedly vaccinated with B. abortus strain-19 vaccine the in vitro test classified 3 animals as positive whereas the skin test identified all the animals as infected during most of the experimental period. Four heifers injected with a single dose of B. abortus strain 19 were consistently negative to the lymphocyte transformation test while the skin test classified all the animals as infected during most of the experimental period. The skin test gave strong reactions indicative of Brucella infection in heifers vaccinated with 'Duphavac' and 'Abortox' vaccines whereas the lymphocyte transformation test was consistently negative with these vaccines. The two tests were negative in unexposed cattle. It was concluded that the in vitro test correlated better with Brucella isolation than the in vivo test did and that the lack of agreement between the results of the two tests is likely to be due to the different antigens used in the assays.

The anticoagulant rodenticide flocoumafen was tested against warfarin-resistant Norway rats (Rattus norvegicus Berk.) infesting farm buildings. Complete control was obtained in 10-21 days (mean 14.2 days) in six treatments in which baits poisoned with 0.005% flocoumafen were maintained, in surplus, until rats ceased to feed from them. A further six treatments, in which the application of poisoned bait was restricted to periodic placements of 50 g, were also completely successful in 15-30 days (mean 21.0 days). Less poisoned bait was used in the restricted flocoumafen treatments than in the unrestricted treatments but the time taken to control the rat infestations was significantly longer.

Young adult mice were inoculated intravenously with strains JB or Peter C of Mycoplasma pulmonis. A few were inoculated intranasally with strain JB. This strain but not Peter C was isolated for 50 days or more from the urines of more than half of the mice. Those of strains TO, C3H and CBA, but not CFLP, were susceptible. Recovery of mycoplasmas was intermittent and sometimes the numbers isolated varied within individual mice and between mice of a particular strain, ranging from 5 X 10(1) to greater than or equal to 5 X 10(7) colour-changing units/ml. Fifty serial passes of M. pulmonis, strain JB, in mycoplasmal medium resulted in attenuation, the organisms after inoculation of TO mice not being recovered from the urine and excretion not being stimulated by treating the mice with progesterone. At autopsy, the organisms of early passage were usually but not invariably isolated from the kidneys of mice that had been urinary excretors. About half of the latter had no renal histopathological changes. The others had usually minimal renal perivascular lymphocytic infiltrates but occasionally more widespread inflammatory changes. The findings may have relevance to the spread of mycoplasmal infection within mouse colonies and suggest that an association between such infection and nephritis in other species, including man, should be sought more closely.

DNA restriction endonuclease analysis was used for intra-specific typing of Mycobacterium bovis isolates from 83 brush-tailed possums (Trichosurus vulpecula) obtained between 1982 and 1984 from the three major regions in New Zealand with endemic bovine tuberculosis. All the isolates were found to be genetically very similar. Differentiation of the isolates into 33 restriction types was achieved by using high-resolution electrophoresis and the combined results from separate digestions with the restriction enzymes Bst EII, Pvu II and Bcl I. The typing system was entirely reproducible. Isolates of the same type were usually found in adjacent localities and were always limited to one of the three major regions. In some cases, isolates of the same type were found in both 1982 and 1984. The phenotypic significance of the small genetic differences identified between different isolates is unknown. The typing system will be useful for monitoring the transmission of M. bovis to other species and the future spread of different M. bovis types through possum populations.

Four groups of sows were inoculated, either once or twice, with O1BFS 1860 foot and mouth disease oil-emulsion vaccine during pregnancy and samples of serum, for analysis, were collected at intervals for greater than 300 days. The pregnant sows responded well to vaccination regardless of their state of gestation. Single vaccination produced protective levels of antibody (greater than 1.53 log10SN50) in 3 out of 4 sows while double vaccination produced protective levels in all 6 sows tested. Anti-FMD IgM antibodies could be detected for 40-60 days after vaccination or revaccination. Anti-FMD IgG antibodies appeared within 10 days of vaccination and persisted, in each sow, for the duration of the study. The anti-FMD IgA response observed was less easy to characterize due to significant animal to animal variation. Although there was no evidence of a fall in the neutralizing antibody titres over one year post vaccination the anti-FMD IgG antibody population did show signs of a change in its heterogeneity and avidity.

Virus of the bluetongue (BT) serogroup was recovered from 11% of cattle sera collected from apparently healthy animals in Khartoum Province for the sole purpose of screening for BT antibodies. Since these sera did not contain BT antibodies, the donor cattle could have been scored as BT free in the serological survey. Virus was initially isolated in chicken embryos inoculated intravascularly, and was further adapted to Vero cell cultures. Isolates were identified as belonging to the BT serogroup using the agar gel immunodiffusion (AGID) and complement fixation (CF) tests. The results indicated that cattle in the Sudan could harbour BT virus without showing symptoms of the disease. Such an observation necessitates further work to clarify the role of cattle in the epidemiology of BT in the Sudan.

An enzyme-linked immunosorbent assay (ELISA) was developed to detect IgG antibodies to diphtheria toxin in human serum. Serum samples obtained from 557 normal persons aged 1-65 years from different areas in New Zealand showed maximum antibody levels in the 1-9 years age group (95.1%) and the least in the 60-65 years age group (38.1%). The indirect ELISA is suitable for seroepidemiological survey study as it is simple to perform, economical and precise.

The anticoagulant rodenticide flocoumafen was evaluated against Rattus rattus and Bandicota bengalensis. In no-choice 24 h feeding tests 100% mortality occurred at 0.00125% concentration of the poison in the bait in the case of B. bengalensis and at 0.00375% in R. rattus. Feeding of 0.0025% poison bait in 1-day, no-choice and 2-day choice tests resulted in 60% and 75% mortality of R. rattus, respectively, and 100% of B. bengalensis. The differences between the consumption of plain food in the pretreatment period and of poison bait in no-choice tests were non-significant, except in one case. The rodents consumed significantly more (P less than 0.01) poison bait than the plain alternative in the choice trials. Median period of survival and its 95% confidence limits of R. rattus and B. bengalensis, at the 100% mortality dose levels of the poison, were 6.3 (5.04-7.88) and 6.2 (4.92-7.81) days respectively.

Enzyme immunoassays (ELISA) have been developed for the detection of BK virus IgG- and IgM-antibodies. Specific IgG is detected by an antigen-coated solid phase test; IgM by an antibody capture method. These methods have been used to study the age-distribution of BK virus antibodies in Tromsø county in Northern Norway. The serum panels tested were: 60 sera from paediatric patients aged 0-1 year; 220 sera from healthy persons aged 1-82 years; 74 sera from healthy blood donors; 107 sera from healthy pregnant women. The age-distribution of BKV-IgG antibodies showed that primary infections took place predominantly between the ages of 1 and 6 years, and that there were no sex differences, either in the age-specific prevalence or in the level of BKV-IgG. We found no significant differences in the prevalence of BKV-IgM antibodies in healthy children and adults and pregnant women. BKV-IgM was detected in 26 of the 461 sera tested (5.6%).