Immunity to leptospirosis: antiserums in dogs and hamsters.

Resistance to clinical and renal leptospirosis in dogs injected with antiserum to Leptospira interrogans serotype canicola and Leptospira interrogans serotype icterohaemorrhagiae was demonstrated. The relationship between resistance induced in serum-injected hamsters was also demonstrated, using criteria of leptospiremia, renal infection, leptospiruria, and clinical signs of disease in dogs and death in hamsters.     

Immunity to leptospirosis: bacterins in dogs and hamsters.

Resistance to clinical and renal leptospirosis in dogs vaccinated with a bacterin containing Leptospira interrogans serotype canicola and Leptospira interrogans serotype icterohaemorrhagiae was demonstrated. The relationship between resistance induced in vaccinated dogs and that induced in vaccinated hamsters was also demonstrated, using criteria of leptospiremia, renal infection, leptospiruria, and clinical signs of disease in dogs and death in hamsters.     

Transmission of foot-and-mouth disease by vaccinated cattle following natural challenge

Cattle vaccinated with a conventional monovalent type O1 foot-and-mouth disease (FMD) vaccine were challenged between four and 21 days after vaccination by short-term exposure to homologous airborne virus produced by pigs. Transmission was then assessed by housing susceptible cattle with the vaccinated animals and testing and observing all the animals for signs of infection and clinical disease. All 18 cattle vaccinated three weeks before challenge resisted clinical disease and although four contracted subclinical infection, there was no transmission to susceptible cattle in contact. One of the two groups of cattle vaccinated two weeks previously transmitted subclinical infection, but not disease, to susceptible animals housed with them from day 0 after challenge. Subclinical infection was manifested by a transient viraemia which was not followed by a detectable circulating antibody response. Shorter periods (seven or four days) from vaccination to challenge resulted in transmission of disease from clinically normal vaccinated to in-contact animals in one of two experiments. The severe challenge presented by the diseased in-contact animals than overwhelmed the immunity of the vaccinated animals. The results indicate that during emergency vaccination programmes it is advisable to vaccinate all FMD-susceptible animals within the vaccination zone and that at the outer boundary of the zone vaccinated animals should be kept separated from unvaccinated animals for at least three weeks.     

Immunity of ivermectin treated cattle to challenge from helminth parasites in the following season

Two groups of yearling cattle which had been treated with ivermectin either three and eight, or three, eight and 13 weeks after turn out to trichostrongyle contaminated pasture in their first grazing season were exposed in the following season to natural challenge with helminth parasites. To assess their immunity to this challenge each group shared a pasture with parasite naive first season calves. No anthelmintic treatments were administered at any time during the year. Throughout the grazing period the yearlings showed normal respiratory rates, negative faecal lungworm larval counts, and, relative to the calves, low faecal trichostrongyle egg counts. All the first season calves developed patent lungworm infections and on one occasion the mean respiratory rates of each group of calves were significantly greater than those of the yearling cattle. At the end of the grazing period, from early May until late September or October 1986, the cattle were removed from pasture and together with parasite naive controls challenged with either 10 or 22 third stage larvae of Dictyocaulus viviparus/kg bodyweight and necropsied between 18 and 23 days later. Although the experimental challenge resulted in relatively heavy lungworm infection of the naive controls, none of the yearlings and only three of the 11 calves which had been at pasture were found to be infected. However, large numbers of arrested fourth stage larvae of Ostertagia ostertagi were present in all the naturally infected yearlings and calves.     

Serum sialic acid and oxidative stress parameters changes in cattle with leptospirosis

This study was designed to disclose some indicators of oxidative stress and inflammation in natural cases of bovine leptospirosis. For this purpose, 12 bulls exhibiting clinical signs of leptospirosis and 10 healthy bulls were used. Animals were subjected to thorough clinical examination and the clinical signs were recorded. All animals were blood sampled in order to determine serum total sialic acid (TSA), lipid bound sialic acid (LBSA), malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO), uric acid (UA), total protein (TP), albumin and glucose. Urine samples were collected from each animal and examined under dark-field microscope to observe spirochetes. Diseased animals exhibited clinical signs suggesting leptospirosis and the diagnosis was supported by positive dark-field microscope examination. Mean TSA (mmol/L), LBSA (mmol/L), TP (g/dl), albumin (g/dl), glucose (mg/dl), MDA (μmol/L), GSH (mg/dl), NO (nmol/ml), and UA (mg/L) levels were 1.63 ± 0.02, 0.40 ± 0.10, 7.18 ± 0.24, 3.23 ± 0.5, 64.96 ± 1.88, 5.71 ± 0.11, 78.68 ± 0.72, 7.94 ± 0.34, and 8.75 ± 0.41 in healthy bulls, and 2.50 ± 0.05, 0.70 ± 0.2, 9.27 ± 0.17, 2.55 ± 0.62, 107.93 ± 2.52, 8.82 ± 0.14, 47.85 ± 1.85, 14.57 ± 0.63 and 15.85 ± 0.80 in leptospirosis cases, respectively. The differences between the two groups were statistically significant (P < 0.001). Increased TSA, LBSA, MDA, NO, UA, TP, glucose and decreased GSH and albumin concentrations were suggestive of inflammation and oxidative stress in diseased bulls. The results obtained may suggest that oxidative damage along with other mechanisms might have taken part in the pathogenesis of bovine leptospirosis and further detailed studies are needed to fully understand the mechanism(s) of the disease.     

Immunoglobulins in cattle vaccinated with leptospiral bacterins.

The growth-inhibition test was used to detect specific antibodies against Leptospira interrogans serotype hardjo in isolated immunoglobulin (IgG and IgM) fractions of serums from cattle vaccinated with leptospiral bacterins. The growth-inhibiting antibodies were detected mainly in the IgG class. Agglutinated clumps also occurred with the IgM fraction. The serums collected from cattle 4 months after vaccination were negative in the microscopic agglutination test.     

Neural changes in vaccinated calves challenge exposed with virulent infectious bovine rhinotracheitis virus

Recurrent infection in calves vaccinated with infectious bovine rhinotracheitis-(IBR) modified live virus was induced by dexamethasone (DM) treatment given 49 days after challenge exposure with virulent IBR virus. Nonchallenge-exposed IM and intranasally vaccinated calves did not excrete the virus after DM treatment; however, IM and intranasally vaccinated and subsequently challenge-exposed calves excreted the challenge-exposure virus into the nasal secretions 5 to 11 days and 6 to 10 days after the DM treatment, respectively. The calves were killed 15 to 18 days (experiment 1) and 14 days (experiment 2) and DM treatment was started and then were examined by histopathologic and fluorescent antibody techniques. All DM-treated calves that were inoculated with the vaccinal virus and challenge exposed with the virulent virus developed nonsuppurative trigeminal ganglionitis and encephalitis. On the contrary, the DM-treated nonchallenge-exposed vaccinated calves did not have lesions in the peripheral nervous system and CNS. Infectious bovine rhinotracheitis virus antigens were not observed in tissues of any of the calves examined (experiments 1 and 2) by fluorescent antibody techniques. These observations indicated that the modified live IBR virus neither produced lesions nor induced latent infection and that modified live IBR virus vaccination did not protect the calves against the establishment of a latent infection after their exposure to large doses of the virulent IBR virus.     

Serological studies on leptospirosis in cattle in east central Alabama.

Serological surveys of leptospiral antibodies in cattle were carried out in Macon and the surrounding counties of East Central Alabama. A total of 286 bovine serum samples were screened for the presence of antibodies against live antigens from twelve pathogenic leptospiral serotypes using a microscopic agglutination test. The most frequently encountered serotypes were Leptospira hardjo (47%), Leptospira wolffi (34%), Leptospira canicola (12%), Leptospira pomona (10%) and Leptospira ballum (10%). Leptospira autumnalis, Leptospira grippotyphosa, Leptospira icterohemorrhagiae, Leptospira pyrogenes and Leptospira tarassovi were observed in less than 5% of the samples.     

Bovine leptospirosis: Microbiological and histological findings in cattle slaughter

Kidneys from cattle at slaughter were examined for the presence of leptospires. Of 218 (8.3%) kidneys leptospires were isolated from 18; all were identified as Leptospira interrogans serovar hardjo. None of the leptospire-infected kidneys had histopathological lesions indicative of leptospirosis and leptospires were demonstrated in only 2 by immunogold silver staining. Leptospires infected kidneys remained viable for at least 21 days when stored at 4 degrees but became non-viable within 14 days when stored frozen at -15 degrees.