'Leptorapide' - a one-step assay for rapid diagnosis of human leptospirosis.

SUMMARY: Leptospirosis is a globally important zoonotic infection caused by spirochaetes of the genus Leptospira. It is transmitted to humans by direct contact with infected animals or indirectly via contaminated water. It is mainly a problem of the resource-poor developing countries of the tropical and sub-tropical regions of the world but outbreaks due to an increase in travel and recreational activities have been reported in developed and more industrialized areas of the world. Current methods of diagnosis are costly, time-consuming and require the use of specialized laboratory equipment and personnel. The purpose of this paper is to report the validation of the 'Leptorapide®' test (Linnodee Ltd, Northern Ireland) for the diagnosis of human leptospirosis. It is a simple one-step latex agglutination assay performed using equal volumes of serum sample and antigen-bound latex beads. Evidence of leptospiral antibodies is determined within minutes. Agglutination is scored on a scale of 1-5 and the results interpreted using a score card provided with the kit. Validation has been performed with a large sample size obtained from individuals originating from various parts of the world including Brazil and India. The test has shown sensitivity and specificity values of 97·1% and 94·0%, respectively, relative to the microscopic agglutination test. The results demonstrate that Leptorapide offers a cost-effective and accurate alternative to the more historical methods of antibody detection.

Stillbirth/perinatal weak calf syndrome: preliminary pathological, microbiological and biochemical findings.

Microbiological, biochemical and pathological data collected from 293 calves which were either stillborn, or born alive and either failed to breathe or failed to breathe for more than about 10 minutes are presented. No bacteria were recovered from 96 of the calves (32.7 per cent), and bacteria which were considered significant were isolated from only four (1.4 per cent). Evidence of leptospiral infection was found in 75 calves (25.5 per cent). Of 64 calves examined for bovine virus diarrhoea (BVD) and infectious bovine rhinotracheitis (IBR) antigens, two were positive for BVD virus and none for IBR virus. The mean (+/- sd) liver vitamin E and kidney selenium concentrations, determined in 148 of the calves, were 2.0 +/- 0.76 micrograms/g wet matter and 0.47 +/- 0.17 micrograms/g wet matter, respectively. The thyroid iodine concentration in 15 of 71 calves (21 per cent) was less than 300 micrograms/g wet matter and the mean (+/- sd) thyroid weight of 266 of the calves was 18.5 +/- 11.6 g. Evidence of severe trauma was found in 19 of the calves (6.5 per cent). Histological findings included thyroid epithelial hyperplasia, hepatic haemosiderosis, erythrophagocytosis in the spleen, perivascular haemorrhage in brain and adrenal glands, and accumulation of leucocytes in blood vessels.

Antibiotic sensitivity of bovine staphylococcal and coliform mastitis isolates over four years.

Eight hundred and forty-eight strains of Staphylococcus aureus and coliforms isolated from milk samples taken from cows with clinical or subclinical mastitis were tested for their sensitivity to a range of antibiotics, comparing strains isolated in 1984, 1985, 1986 and 1987. The only increase in the proportion of resistant strains occurred with coliforms resistant to ampicillin and neomycin.

Isolation of mycoplasmas from bovine semen in Northern Ireland.

In a survey of 332 fresh and 137 processed bovine semen samples and 25 preputial washes, mycoplasmas and, or, ureaplasmas were isolated from 46 per cent, 31 per cent and 80 per cent, respectively. Intermittent isolation from different semen collections from the same bull indicated that at least three collections per bull were necessary to determine whether infection was present. When stored processed samples were examined Mycoplasma canadense and M bovigenitalium were isolated from straws taken as long ago as 1975. Addition of lincomycin and spectinomycin to the semen extender eliminated the isolation of mycoplasmas and reduced the rate of isolation of ureaplasmas.

Mycoplasma californicum mastitis in ewes as an experimental model for antibiotic treatment.

A strain of Mycoplasma californicum successfully infected an experimentally inoculated ovine mammary gland causing a severe mastitis. The condition lasted for about 25 days, and resulted in atrophy and loss of milk production in the gland. Four experimentally infected ewes, treated over a 3-day period with various regimes of the antibiotics oxytetracycline or tylosin during the acute stage of infection, successfully eliminated the infection. Two others similarly treated with combined intramammary and intramuscular tiamulin or with intramammary Bay Vp2674, did not eliminate the infection; but another ewe treated with intramuscular as well as intramammary Bay Vp2674, did resolve the infection. The two ewes that were unsuccessfully treated with antibiotics at the acute stage did respond to tylosin or oxytetracycline at a later stage of infection. Measurement of antibiotic concentrations demonstrated that the persistence of inhibitory levels in the milk varied between the antibiotics and were influenced by the extent of parenteral treatment.

The potential of the ovine udder as a model to determine the pathogenicity of bovine ureaplasmas.

Various methods of inducing mastitis in the ovine mammary gland with two bovine ureaplasma strains were investigated. The most successful method was by inoculation of fresh broth cultures on two successive days, 24 h apart. Eight more bovine strains were inoculated by this means and three successfully infected the glands.

Effect of vaccination of the dam on rotavirus infection in young calves.

Vaccination of cows with a combined, inactivated, adjuvanted rotavirus and Escherichia coli vaccine resulted in increased neutralising antibody titres to rotavirus in serum and colostral whey. Evidence was obtained that vaccination resulted in a decreased incidence of rotavirus shedding and of abnormal faeces or diarrhoea in young calves fed colostrum and milk from the vaccinated dams. The E coli component of the vaccine was not evaluated because no natural challenge was evident.

Phage typing of Staphylococcus aureus associated with subclinical bovine mastitis.

Six hundred and seventeen isolates of Staphylococcus aureus from subclinical clinical mastitis cases in 63 dairy herds in Northern Ireland were typed using a set of 25 phages. Ninety-four per cent of the isolates were typable, with nine phages, predominantly from groups I and III, being responsible for almost all of the lysis. Although 68 phage patterns were found, six of them typed 47.2% of the isolates. One strain accounted for 14.7% of the isolates, but the largest number of strains (44) was restricted to individual farms. The epidemiological significance of these findings for on-farm mastitis control is discussed.

Mycoplasma californicum mastitis in the dry dairy cow.

Mastitis in 85 of 140 dry cows and 16 of 101 milking animals on one farm was shown to be caused by Mycoplasma californicum. The infection was eradicated from the herd over a five month period by a combined programme of identification, segregation and culling of infected animals. Some dry cows produced a self-cure, but the majority calved with nonfunctional quarters which produced very little colostrum and resulted in a high incidence of calf mortality. The source of the infection could not be established, but it was probably spread in the dry cows by the unhygienic application of long acting intramammary antibiotic therapy.

Changes in immunoglobulin levels in whey during experimental Streptococcus agalactiae mastitis.

Total protein and immunoglobulin levels in the wheys of eight first lactation heifers, four vaccinated and four unvaccinated, were measured during three consecutive experimental intramammary infections with Streptococcus agalactiae. There were no significant differences between infections 1, 2 and 3 in the protein or immunoglobulin content of the uninfected quarters. Peak whey total protein of the infected quarters came earlier with each infection, until by the third they were seen after eight hours. During this acute phase a reversal of the normal milk IgG1/IgG2 ratio in all infected quarters was measured. Increases in whey IgA and IgM in the infected quarters of the vaccinates were also noted. A similar response only occurred following the third infection of the unvaccinated animals. All whey immunoglobulin levels returned to normal by 48 hours after infection, after which only IgG1 levels increased in infected quarters.

The loss of opsonic activity of bovine milk whey following depletion of IgA.

The role of the IgA antibody to Streptococcus agalactiae found in the whey of milks 12 hours after the first intramammary infection of six Friesian first lactation heifers was assessed using an in vitro bactericidal assay. The mean percentage kill of the streptococci by neutrophils in the presence of these wheys was 36.2% while the equivalent figure for the non-infected quarter whey was 0%. When the IgA antibody was absorbed from the infected quarter wheys using class specific IgA antiserum cross linked with glutaraldehyde the percentage kill of the test system fell to 0%. Elution of the absorbed antibody partially restored the activity to a mean percentage kill of 18.2%. The results indicated that the IgA antibody found in infected quarter whey during the acute stages of intramammary infection with Streptococcus agalactiae was responsible for the opsonic activity which pertained at that time.

Coronavirus infection of the bovine respiratory tract.

Two viruses, morphologically resembling coronaviruses and antigenically indistinguishable from bovine enteric coronavirus, were isolated in bovine tracheal organ cultures from the lungs and trachea of young calves with respiratory disease. Intranasal and intratracheal inoculation of these viruses into neonatal calves resulted in a predominantly upper respiratory tract infection, which was associated with the development of mild respiratory symptoms.