Usefulness of Stress Indicators in Forecasting Population Trends in Microtus arvalis (Pallas)1

The appearance of a stress condition in Microtus arvalis (Pallas) populations was established on the basis of histochemical analyses and correlated with population dynamics. It was found that stress appears only during invasions, i.e. when crop damage has already occurred. Commonly, the population crash occurs 30 to 50 days after the appearance of stress. It is concluded that stress indices can neither be used for warnings nor for long-term forecasts of outbreaks.     

Antigenic relationship of non-serotype 1 turkey infectious bursal disease viruses from the United States and United Kingdom

Cross-neutralization tests showed that non-serotype 1 infectious bursal disease viruses originating from turkeys in the United States and the United Kingdom belong to the same serotype. It is proposed that this serotype be designated serotype 2.     

Protection of turkey poults from Bordetella avium infection and disease by pili and bacterins

The role of pili in protection against Bordetella avium infection in turkey poults was studied. An isolate that produced the largest number of pili under growth conditions developed in our laboratory was used for preparation of pili and bacterin and for challenge. The pili were isolated, purified, examined by electron microscopy, and tested for purity by gel electrophoresis. Poults were vaccinated with oil-adjuvant pili, formaldehyde- or merthiolate-inactivated bacterins, or a commercial bacterin. Poults were vaccinated once or twice subcutaneously at different ages and challenged intranasally with a pathogenic B. avium isolate 5 days following the last vaccination. A few vaccinated birds had very mild clinical signs. B. avium was isolated from the sinuses of a few vaccinated birds, and growth was scanty. The mean colony counts from tracheal sections was significantly higher (P less than 0.1) in unvaccinated challenged poults than in vaccinated challenged poults. It is postulated that B. avium pili are important immunogens in turkey poults.     

Nucleic acid and structural proteins of infectious bursal disease virus isolates belonging to serotypes I and II

The nucleic acid and structural proteins of infectious bursal disease virus serotype I (six isolates) were compared with those of serotype II (two isolates). Five of the serotype I isolates originated from chickens, whereas both serotype II isolates were from turkeys. The growth curves of representative isolates of both serotypes were similar, but the latent period and virus yield were different. The seven isolates tested had two segments of double-stranded genomic RNA. The RNA migration patterns of viruses belonging to each serotype were similar, but differences were noticed between the two serotypes. There were differences in the molecular weights of viral proteins (VP) 3 and 4 from the two serotypes, and serotype II isolates lacked VP-2.     

Rotavirus as a cause of diarrhea in pigs.

A rotavirus (reovirus-like agent) was associated with diarrheal diseases occurring in 1- to 4-week-old suckling pigs in 8 herds and in weaned pigs in 2 herds. Transmissible gastroenteritis virus was also detected in 2 of these herds, as was enteropathogenic Escherichia coli in 5 herds. Morbidity was generally greater than 80% in pigs of the affected age group within these herds, and mortality from diarrhea ranged from 7 to 20%. The disease due to rotavirus in suckling pigs appeared similar to the syndrome commonly referred to as milk scours, white scours, or 3-week scours. Diarrhea and villous atrophy, resembling that seen in transmissible gastroenteritis, occurred in naturally infected pigs and in gnotobiotic pigs experimentally infected with rotavirus. Diagnosis was accomplished by immune electron microscopy of intestinal contents and by immunofluorescent staining of enterocytes. A massive infection of enterocytes with rotavirus was demonstrated by immunofluorescence, which helps explain the pathogenesis of this disease. The apparent rarity of clinical rotaviral infections in suckling pigs greater than 7 days old is probably due to the acquisition of passive immunity from immune sows.     

Immune electron microscopy of transmissible gastroenteritis virus and rotavirus (reovirus-like agent) of swine.

Immune electron microscopy (IEM) was developed as a diagnostic aid for detecting and identifying transmissible gastroenteritis virus and rotavirus (reovirus-like agent) in fecal and intestinal contents from cases of gastroenteritis in young pigs. Variables involved in use of direct IEM and its sensitivity were determined. Aggregates of virus coated with specific antibody were seen in virus samples mixed with homologous convalescent antiserum, but not in control samples containing preexposure serum or antibody directed against a heterologous virus. At least a ten fold enhancement of the sensitivity of direct IEM for virus detection was accomplished using indirect IEM employing rabbit anti-porcine IgG to further aggregate virus-antibody complexes. The technique was used to investigate the size and morphology of the porcine rotavirus. Particles ranged from 55 to 70 nm in diameter and had capsomere structures. Morphologically, the porcine rotavirus resembled the calf and human rotaviruses. By IEM, employing specific antiserums for each virus, porcine rotavirus was found to be antigenically related to these 2 viruses, but not to the reovirus type 3.     

Isolation and characterization of Bordetella avium plasmids

Experiments were conducted to study the plasmids of Bordetella avium, B. avium-like, and B. bronchiseptica isolates from turkeys and the plasmids of the Art-Vax commercial vaccine strain. Plasmids were observed in 6 of 20 B. avium isolates, in 6 of 20 B. avium-like isolates, in all 5 B. bronchiseptica isolates, and in the Art-Vax strain. Plasmids of B. avium correlated with resistance to antibiotics but not with pathogenicity, hemagglutination of guinea pig erythrocytes, or expression of pili.     

Antigenicity of two turkey astrovirus isolates

Astroviruses are positive-sense single-stranded RNA viruses. These viruses cause gastroenteritis in humans and in a variety of animal species, including turkey poults. Only human astroviruses are well characterized antigenically. In the current study, two turkey astrovirus isolates, TAstV1987 and TAstV2001, were antigenically compared using cross-neutralization tests in turkey embryos, as well as cross-reactivity of the two isolates by an enzyme-linked immunosorbent assay (ELISA). The antigenic relatedness values (R) were calculated using the Archetti and Horsfall formula. The R value based on the cross-neutralization tests was 0.56%, which indicates that TAstV1987 and TAstV2001 belong to different serotypes; the R value of the two viruses based on ELISA was 70.7%, which suggests these two viruses share common antigen(s).     

Glanders--a comprehensive review

Since 1990 the number of glanders outbreaks in race, military and pleasure horses in Asia and South America is steadily increasing. Glanders, which is eradicated in Western Europe, Australia and Northern America, is currently considered a re-emerging disease. Consequently, the disease may be introduced into glanders-free regions by subclinical carriers at any time. The causative agent of glanders, Burkholderia (B.) mallei, is highly contagious and leads to chronic disease in horses whereas in donkeys and mules the disease is acute and often fatal. Occurrence of the disease leads to international trading restrictions and infected animals immediately have to be culled and safely disposed off. In humans B. mallei infection results in a severe clinical course, and is fatal without appropriate therapy. Its pathogenicity makes B. mallei a potential biological agent that may be used in bioterroristic attacks. Due to the eradication of glanders in the second half of the last century, veterinarians in western European countries are no longer familiar with its clinical presentation in solipeds. Having these facts in mind, this review describes the epidemiology, clinical signs, pathology and the current eradication strategy of this interesting zoonosis. Pictures of imported endurance horses infected with glanders taken during an eradication campaign in Dubai, United Arab Emirates, in 2004 illustrate most typical clinical findings.