Eric Cox

INCIDENCE AND SIGNIFICANCE OF ISOLATION OF MYCOPLASMA FELIS FROM CONJUNCTIVAL SWABS OF CATS

Conjunctival swabs taken from 40 cats with conjunctivitis and 65 cats without conjunctivitis were examined for the presence of Mycoplasma felis. The incidence of M. felis in cats with conjunctivitis was 25%. M. felis was not isolated from clinically normal cats. Inoculation of two isolates into the conjunctival sacs of healthy cats induced conjunctival hyperemia, starting 2-3 days after inoculation and disappearing without treatment within 7 days. It is concluded that M. felis plays a role in feline conjunctivitis.

Intestinal protection against challenge with transmissible gastroenteritis virus of pigs immune after infection with the porcine respiratory coronavirus

Abstract An infection of pigs with the porcine respiratory coronavirus (PRCV) induces antibodies which neutralize the enteropathogenic transmissible gastroenteritis virus (TGEV) and PRCV to the same titre. In the present study, 10-week-old seronegative pigs (n = 8), pigs immune following TGEV inoculation (n = 4) or pigs immune following aerosol (n = 8) or intragastric inoculation (n = 4) with PRCV were challenged with TGEV. Whereas TGEV-immune pigs were completely protected against challenge, all PRCV-immune pigs showed serological evidence of TGEV replication. Nevertheless, the aerosol or intragastric inoculation with PRCV primed the humoral immune system against TGEV and the TGEV challenge induced a secondary antibody response in most PRCV-immune pigs. Furthermore, all PRCV-immune pigs showed a decrease in the duration of the excretion of infectious TGEV (0–4 days) in comparison with the duration of the virus excretion by seronegative pigs (5–6 days).

Effect of experimentally-induced villus atrophy on adhesion of K88ac-positive Escherichia coli in just-weaned piglets

Abstract Three- to four-week-old, just-weaned piglets were infected with transmissible gastroenteritis (TGE) virus and the next day with K88ac+ enterotoxigenic Escherichia coli (ETEC). Histological examination of caudal jejunum and ileum of piglets killed 2–3 days after virus challenge (1–2 days after ETEC infection) revealed severe villus atrophy especially in the jejunum compared with controls (P<0.05). Four-5 days after TGE virus infection villus length increased and after 7 days it was near normal. Villi scraped from jejunal and ileal mucosa of the piglets were incubated in vitro with K88ac+ E. coli and the number of bacteria adhering to 250 μm villus brush border was counted. Attachment of bacteria to villi of piglets killed 2–3 days after TGE virus infection was significantly decreased in comparison with adhesion to villi of non-infected piglets or of piglets killed 7 days after the virus infection. Correlation between in vitro adhesion and villus height was 0.6649 (P<0.001). The results suggest that the experimentally-induced villus atrophy was attended with a temporarily diminished susceptibility of villus enterocytes to adhesion of K88ac+ E. coli.

A sero-epizootiological study of porcine respiratory coronavirus in Belgian swine.

A porcine respiratory coronavirus (PRCV), antigenically closely related to transmissible gastroenteritis virus (TGEV), appeared in the European swine population in 1984. The present serological study was performed to obtain insight into the epizootiology of PRCV and of TGEV. PRCV-induced neutralizing antibodies were found in 90.6 per cent of the 160 sera collected from sows at slaughter, demonstrating the enzootic appearance of PRCV in the Belgian swine population. A serological study of fattening swine on 33 farms revealed that 11 farms situated in an area with a high farm density (all farms within 4 km2) and 11 on 22 closed breeding-fattening farms situated in areas with a low farm density (only one to four farms per 12 km2) were infected with PRCV throughout the year, whereas the other 11 closed breeding-fattening farms were temporarily free of PRCV. PRCV disappeared from the farms mainly in spring and summer. All the 11 farms became reinfected in autumn or winter, indicating that PRCV is regularly reintroduced in farms in the colder seasons. There was no correlation between the herd size and the temporary disappearance of PRCV from farms. It was observed on some farms that PRCV could infect pigs shortly after weaning in the presence of declining maternal antibodies, indicating that PRCV can persist on a farm by regularly infecting newly weaned pigs. TGEV-specific antibodies were found in 7.6 per cent of the 160 sera from the slaughterhouse sows. TGEV-specific antibodies were also detected in sera from fattening swine of 5 of the above mentioned 33 farms. TGEV-outbreaks were not observed on these farms.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of Milk IgA Antibodies by Porcine Respiratory Coronavirus Infection

An ELISA was developed to examine the prevalence of TGEV-specific immunoglobulin (Ig)A in the milk of sows, infected in the field with PRCV or with TGEV. It was shown that previous PRCV-infections can induce the secretion of IgA antibodies in the milk. However, only 9 out of 28 PRCV-infected sows had IgA in their milk whereas 11 TGEV-infected sows all secreted IgA. On farms where a reinfection with PRCV occurred, the number of IgA-secreting sows increased from 2 to 11 on a total of 13 sows. This showed that the presence of IgA antibodies in the milk may depend upon the occurrence of reinfection with PRCV. As demonstrated by density gradient analysis, the milk IgA induced by PRCV was 11S secretory IgA and had the capacity to neutralize TGEV.