Passive protection of calves against experimental infection with Salmonella typhimurium

Cows were vaccinated with formalin-killed Salmonella typhimurium approximately seven weeks and two weeks before parturition to investigate whether passive immunity could protect their calves against experimental S typhimurium infection. After birth the calves were left with their dam for 48 hours and then separated and fed cold, stored colostrum from their own dam for a further eight days. Oral challenge five days after birth with 10(8) S typhimurium did not result in the death of these calves even when they had absorbed little colostrum. Mortality was reduced to 22 per cent in calves which sucked from vaccinated dams and were then fed colostrum from unvaccinated cows and to 50 per cent in calves born to unvaccinated cows and later fed colostrum from vaccinated animals. Calves which sucked from a vaccinated dam and then received stored colostrum from the same cow excreted salmonellas for significantly shorter periods after challenge and were less often infected at necropsy 28 days after inoculation. Protection was not correlated with the levels of O or H agglutinating antibodies in serum, which were at a maximum 24 hours after sucking and then slowly declined. There was no evidence of an active antibody response in the serum. Measurement of the O and H response of cows after vaccination indicated that the vaccination schedule could be improved. The highest levels of agglutinating antibody were measured between two and three weeks after the first vaccination and there was only a minimal response to the second vaccination before parturition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative virulence of two porcine group-A rotavirus isolates in gnotobiotic pigs

The virulence of 2 porcine group-A rotavirus isolates was compared. Forty hysterotomy-derived 3-day-old gnotobiotic pigs were inoculated orally with 2 ml of intestinal homogenate containing either the Ohio State University (OSU) or the South Dakota State University (SDSU) strain of porcine rotavirus or were inoculated with medium only. Clinical signs of disease, body weight, distribution of viral antigen, fecal excretion of virus, and histologic lesions (observed by light and scanning electron microscopy) were determined. Morphometric measurements of villi and crypts were made. In pigs inoculated with OSU or SDSU strains, diarrhea began at postinoculation hours (PIH) 19 to 48 and PIH 24 to 54, respectively. None of the virus-infected pigs died as a consequence of infection and all had similar clinical signs of disease, body weight changes, and virus-shedding patterns, regardless of the strain of rotavirus with which they were infected. Microscopic findings in the small intestine of virus-infected pigs were similar, except that the SDSU strain caused more severe villus atrophy and villus fusion in the duodenum at PIH 72 and 168 than was associated with the OSU strain. Viral antigen in the small intestine of pigs infected with either virus was observed by use of immunofluorescence at PIH 24 and 72, but was seldom seen at PIH 168.     

German cockroach resistance: Propoxur selection induces the same resistance spectrum as diazinon selection

A resistant laboratory strain of the German cockroach, Blattella germanica, was developed from a normal laboratory strain by selection with propoxur. Resistance to all insecticides except chlordane began increasing after 15 generations of selection and reached a plateau for most insecticides by generation 27. The resistant colony, designated B-strain, developed significant resistance to carbamates, organophosphorus compounds, pyrethrins and DDT, developed low resistance to gamma-BHC and no resistance to chlordane. The resistance spectrum, effect of synergists and inheritance of resistance of this propoxur resistant strain are similar to a diazinon resistant strain. Therefore, diazinon and propoxur may select for the same resistance mechanism(s) in this species. The practical implications of this research are discussed.     

Changes in body and organ weights of Japanese quail selected for 6‐week body weight 1

Three populations of Japanese quail, selected over 13 generations for increased body weight, a randomly selected base population and reciprocal backcrosses of selected lines to the control were studied. Live body weight and weights of liver, testes, oviducts and carcasses were obtained to assess the effects of selection.

At 6 weeks of age a 20 g. difference in live body weight existed between selected line and base population. Sexual dimorphism in live body weight in favour of females appeared at 3 weeks of age and increased with age. A 5 g. difference in 6‐week body weight between female backcross progeny from sires from selected lines and those sired by males from the base population suggested an influence of sex‐linked genes. At 8 weeks of age the weight of females of both reciprocal back‐cross types significantly exceeded the average of females from the selected lines suggesting that female reproductive organ weight had increased under selection as well as heterosis. Carcass weight of selected females was lower than for corresponding males, a reversal of the sexual dimorphism displayed by the controls.

Reciprocal differences in liver weight between backcross females, but not males, suggested an effect of sex‐linked genes.

Testis as well as oviduct weights of quail from selected lines were substantially greater than from controls.     

Immune responses to non-structural protein 3 (NS3) of bovine viral diarrhoea virus (BVDV) in NS3 DNA vaccinated and naturally infected cattle

Immune responses to non-structural protein 3 (NS3) of bovine viral diarrhoea virus (BVDV) were investigated. cDNA encoding NS3 from type 1a BVDV was used to vaccinate five calves, another five calves remained unvaccinated. Three weeks after final vaccination animals were challenged intranasally with heterologous type 1a BVDV. Anti-NS3 antibodies were detected in only one animal post-vaccination. Partial protection from virus challenge was observed in the vaccinates. Virus was not isolated from nasal mucosa of two vaccinates, and virus clearance from nasal mucosa was faster in the vaccinates compared to the controls. While elevated rectal temperatures were evident in both groups 7 days post-challenge, the mean increase in the controls was twice that observed in the vaccinates. In conclusion, NS3 DNA vaccination induced humoral immunity in one calf, and prevented fever and virus establishment in the nasal mucosa in 2/5 calves, demonstrating the efficacy of NS3 vaccination, which may benefit future development of pestivirus and flavivirus vaccines.     

Spatial relationship between Mycobacterium bovis strains in cattle and badgers in four areas in Ireland

We investigated whether strains (restriction fragment length polymorphism, RFLP-types) of Mycobacterium bovis isolated from badgers and from cattle clustered among and within four areas in Ireland. The spatial scan test and nearest-neighbor analysis were used as the spatial cluster-detection techniques. In addition, for each of the major strains, associations between the distance to badger setts and the "centroid" of the cattle farm were assessed in a logistic model. Overall, between September 1997 and May 2000, 316 and 287 M. bovis samples, from badgers and cattle, respectively, were strain-typed. The distribution of strains in badgers, and separately in cattle, differed among areas. Within each of the four large areas, badgers and cattle tended to have similar strains; this is consistent with the sharing of M. bovis strains within an area. In more detailed within-area analyses, some spatial clusters of M. bovis strains were detected, separately, in both cattle and badgers. Almost half of the infected badger setts with a specific strain were located outside of the "detected" clusters. There was no association between the number of infected badgers with a specific M. bovis strain within 2 or 5 km distances to cattle herds, and the risk of the same strain in cattle. We speculate about the dynamic nature of badger movements, as an explanation for the absence of more clusters of most of the strains of M. bovis isolated from badgers, and its impact on trying to study transmission of M. bovis between cattle and badger.