Leptospirosis in zoo workers associated with bears.

Leptospirosis due to Leptospira interrogans serovar icterohaemorrhagiae was diagnosed in two zoo animal keepers. The implicated source of infection was bear cubs that had microscopic agglutination antibody titers to leptospires of the Icterohaemorrhagiae serogroup.

In vitro studies of haemolysis by Leptospira interrogans serovars pomona and ballum.

Washed and unwashed red blood cells (RBC) from young calves, adult cattle, hamsters and humans were incubated with Leptospira interrogans serovars pomona and ballum. Washed cells suspended in saline were always haemolysed while unwashed cells and those which were washed and resuspended in plasma were never haemolysed, despite the presence of large numbers of organisms within the culture supernatant. Pomona produced greater haemolysis of cattle and human RBC than did ballum, but with hamster RBC ballum produced greater haemolysis than did pomona. A group of 6- to 9-month-old cattle infected with pomona showed no signs of clinical disease and RBC taken from them before infection and during the development of antibodies to pomona were haemolysed by pomona only after the cells were washed. Plasma therefore appears to have a protective function. This in vitro protective function of plasma even extended to plasma from young seronegative calves.

Experimental trials on the use of radioimmunoassay for the detection of leptospiral antigens in urine.

Trials were conducted on the use of the solid phase radioimmunoassay (RIA) to detect leptospires or their antigens in simulated urine samples. The procedure was relatively simple to perform and appeared to be specific in detecting certain numbers of leptospiral organisms or their antigens in experimentally prepared samples. With this technique, it was possible to examine individual or pooled urine samples for the presence of leptospires within half a day. This technique may be of value for the detection of leptospiruric animals if the sensitivity of the technique could be further increased. Suggestions for the improvement of the procedure are discussed.

A rapid latex agglutination test for detection of leptospiral antibodies.

A rapid semi-quantitative latex agglutination test (LAT) has been standardized for the detection of leptospiral antibodies in serum samples of man and animals. The efficacy of the LAT was compared with the plate enzyme linked immunosorbent assay (ELISA). A total of 276 human serum samples were analyzed by both LAT and ELISA and percentage positives were 84.8 and 85.9%, respectively. Similarly, of 65 animal samples tested, 63.1 and 69.2% positivity were observed in LAT and ELISA, respectively. Even though the ELISA test was slightly more sensitive than LAT, the rapidity, simplicity and economics of the LAT were found to fulfill the requirements of a screening test for leptospiral antibodies.

The serological response of calves to Leptospira interrogans serovar hardjo vaccines and infection as measured by the microscopic agglutination test and anti-IgM and anti-IgG enzyme-linked immunosorbent assay.

The microscopic agglutination test (MAT) and the anti-IgM and anti-IgG enzyme-linked immunosorbent assays (ELISA) were used to examine sera taken over the course of 16 weeks from 35 calves vaccinated and/or infected with Leptospira interrogans serovar hardjo. The relationship between the IgM and IgG responses to vaccination and infection were determined. The rapid and high rise in IgM levels following challenge made the anti-IgM ELISA a potentially good indicator of recently established infection although some transitory high levels were seen where infection did not become established. The slow IgG response to infection made the anti-IgG ELISA of limited diagnostic use.

Pathology of acute Leptospira interrogans serotype icterohaemorrhagiae infection in the Syrian hamster.

The pathology of acute Leptospira interrogans serotype icterohaemorrhagiae infection in the Syrian hamster was investigated up to 7 days after infection using histology, electron microscopy and an indirect fluorescence test for leptospires. The disease was characterized by the presence of many leptospires in the tissues, jaundice, leukocytosis, haemorrhages, endothelial alteration and thrombotic glomerulopathy. The leptospires were present intravascularly, in the interstitium penetrating between liver cells and tubular epithelial cells and in the tubular lumina. The presence of leptospires was not necessarily associated with lesions. These findings support both pathogenetic mechanisms suggested in the literature, namely: the ability of leptospires to penetrate actively between cells with detachment of tight junctions, without obvious lesions to the cells, and an immune-mediated process with immune complex formation and binding and activation of complement resulting in leukocytosis, thrombotic glomerulopathy, endothelial alteration and haemorrhages.

Bovine leptospirosis: experimental serovar hardjo infection.

Almost the full range of clinical signs observed in pregnant cattle naturally infected with Leptospira interrogans serovar hardjo was observed in this experimental study in which 22 heifers were infected by intraplacentome inoculation with serovar hardjo strains. These features included abortion, mummification, stillbirth, premature and term birth of weak calves and full-term birth of live apparently healthy calves. Leptospires were demonstrated in all but three calves by culture and or immunofluorescence.

Experimental infection with a Leptospira hardjo strain isolated from cattle of the eastern plains of Colombia.

The infectivity and pathogenicity of a strain of Leptospira hardjo isolated from the eastern plains of Colombia were evaluated. Ten pregnant heifers were artifically inoculated and monitored during 10 months. During the trial, isolation of leptospires was attempted and antibodies were detected by the microscopic agglutination test. Leptospires were recovered from the urine of six of the inoculated animals up to 6 months after infection. Eight of ten calves born from the inoculated heifers were born weak, and one of them died 12 h after parturition. Three of the weak calves had generalized jaundice of the internal surfaces. Half of the cows developed metritis and had a retained placenta. Serological reactions were seen against serotypes other than L. hardjo. A chronic infection was apparently established in the inoculated heifers with leptospiruria resulting in reinfection of the animals and a secondary rise in antibody levels.

Bovine IgM and IgG response to Leptospira interrogans serovar hardjo as measured by enzyme immunoassay.

The enzyme-linked immunosorbent assay (ELISA) was used to detect specific IgG and IgG antibodies in the sera of cattle infected or immunized with Leptospira interrogans serovar hardjo. IgM appeared first but was quickly followed by IgG which persisted longer than IgM. The levels of antibody detectable by ELISA and by the microscopic agglutination test (MAT) did not correlate, suggesting that the two techniques measured different antigen--antibody systems. The transient nature of the IgM response as measured by ELISA indicates potential usefulness as a serodiagnostic test for detecting current leptospiral infections.

Prevalence and geographic origin of pigs with serological evidence of infection with Leptospira interrogans serovar pomona slaughtered in abattoirs in Victoria, Australia.

A set of 10,440 sera was collected from pigs slaughtered at Victorian abattoirs. These sera were subjected to the microscopic agglutination test for antibodies to Leptospira interrogans serovar pomona. Identification of the herd of origin was possible for 6511 pigs, and these were derived from 167 herds in Victoria (84% of sera), from 32 herds in New South Wales (8% of sera) and 29 herds in South Australia (8% of sera). The overall prevalence of titres of 512 and above was 3.7%. This was higher (5.3%) among pigs for which the property of origin was unknown than among pigs with identified properties of origin. Among the latter the prevalence was 2.7% (Victoria 0.6%, New South Wales 1.3%, South Australia 25.2%.) Most of the pigs with unknown properties of origin were derived from market groups and were probably typically from smaller herds. Within Victoria a comparison of results with the known pig populations of the 12 statistical divisions indicated that infection was spread throughout the State. Of the 228 identified herds of origin sampled, 32 (14%) had at least one pig with a high titre. However, this may underestimate the proportion of infected herds, as in many cases only a few serum samples were obtained. Of 73 herds from which 25 or more serum samples were obtained, serological evidence of infection was obtained in 18 herds (25%).

The role of the common vole (Microtus arvalis) in the epidemiology of bovine infection with Leptospira interrogans serovar hardjo.

Control of leptospirosis in cattle depends on the presence of other possible maintenance hosts, with which cattle may have contact. Twenty-seven common voles (Microtus arvalis) were trapped on a dairy farm where the cattle were infected with Leptospira interrogans serovar hardjo (hardjo). In the sera of 11 voles, titres greater than or equal to 100 against serogroup Grippotyphosa were measured with the microscopical agglutination test (MAT). From 8 of these 11 voles, which also showed interstitial lymphoplasmacellular nephritis, Leptospira interrogans serovar grippotyphosa was isolated. We found no evidence that the common vole is a maintenance host for hardjo in this biotope.

Serological study of the frequency of leptospiral infections among dairy cows in farms with suboptimal reproductive efficiency in Galicia, Spain.

Between March 1996 and September 1997, 15 farms located in Galicia (NW Spain) and experiencing suboptimal reproductive efficiency were visited and blood samples were obtained from all the lactating cows (n=442). Additionally, 1060 samples were obtained monthly from a cohort of 219 lactating cows belonging to nine of the farms between March 1996 and April 1997. All the samples were tested by microscopic agglutination (MAT) using live antigens representing the following Leptospira interrogans serogroups: Australis, Autumnalis, Ballum, Canicola, Grippotyphosa, Icterohaemorrhagiae, Louisiana, Pomona, Sejroe, Shermani and Tarassovi. Eighty-one of the 442 cows were positive against one or more serogroups (P=18.33%). Serologically, L. bratislava and L. grippotyphosa were detected as the most prevalent serovars (P=7.92 and 7.69%, respectively) and as the serovars against which the probability of seroconversion was highest (P=0.27 and 0.25, for a 12-month period, respectively) among those studied. The proportional hazards regression method was used for evaluating the seasonal trend of seroconversions against these two serovars. The risk of seroconversion against L. grippotyphosa was significantly higher during spring. The risk of seroconversion against L. bratislava did not differ significantly among seasons. Our results suggest that infections by L. bratislava did not follow, among the study animals and during the study period, the pattern typically described for non-adapted serovars, pointing out the possibility that some strains of this serovar could behave as adapted serovars.

Tears and aqueous humor from horses inoculated with Leptospira contain antibodies which bind to cornea.

An antigenic relationship between Leptospira interrogans and equine cornea was previously described by us. An enzyme-linked immunosorbent assay was employed in the present work to investigate the existence of anti-leptospira and anti-cornea antibodies in tears, aqueous humor and serum from horses inoculated i.m. with those antigens. Ten days after a booster by the same route, antibodies that bind to microtiter plates, coated with an homogenate of either equine cornea or leptospira, were detected in those fluids and in the sera. At the same time, the corneas of the horses began to develop a diffuse opacity. This finding of anti-leptospira antibodies in equine tears and aqueous humor shows the pathway along which they arrive at the cornea and bind to it.

Leptospira interrogans serovars hardjo and pomona: causes of infections in dairy cows and humans in Florida.

Leptospirosis was diagnosed in 11 milkers on 3 dairy farms in a Florida county. Serologic test results identified Leptospira interrogans serovar hardjo as the infecting organism in milkers and cows on one farm, and hardjo was isolated from two cows. On the second farm, serovars hardjo and pomona were implicated serologically in the cows and milkers, and pomona was isolated from two milkers. On the third farm, hardjo infection was identified by serologic tests in one milker, and hardjo was isolated from another.This was the first isolation of hardjo from a human being reported in the United States. Leptospiral infection is an occupational hazard for dairy milkers in some areas of the United States. Thus, the authors recommend that preventive measures should be taken. These measures should include boots and other protective clothing and protection from urine spray for the eyes and nose.

The effect of storage time on isolation of Leptospira interrogans from bovine kidneys.

Kidney tissues from 20 cattle infected with Leptospira interrogans serovars hardjo, pomona, or grippotyphosa were cultured on the day of slaughter and 3, 6, and 8 days later to examine the effect of storage time on the recovery of leptospires by conventional culture methods. Leptospires were isolated from 85% of infected bovine kidney tissues cultured on day 1, and from 95%, 90%, and 90% of kidney tissues stored in transport medium at 4 C for 3, 6, and 8 days, respectively, prior to inoculation of culture media.

Evaluation of an enzyme immunoassay for diagnosis of bovine leptospirosis caused by Leptospira interrogans serovar hardjo type hardjo-bovis.

Sensitivity and specificity of 4 different antigen preparations from Leptospira interrogans serovar hardjo were compared in an enzyme immunoassay for detection of antibodies against serovar hardjo type hardjo-bovis in serum. Two antigens prepared using detergents showed serogroup cross-reactivity. A mechanically extracted membrane and a lipopolysaccharide antigen showed a high degree of leptospiral serogroup specificity. The lipopolysaccharide antigen was the most suitable antigen for detection of anti-hardjo antibodies. Enzyme immunoassay was more sensitive than the microscopic agglutination test for detecting antibodies in serum from experimentally and naturally infected cattle. It was not possible to differentiate vaccinated from infected animals or to detect a secondary immune response in vaccinated animals that were subsequently infected.

Epidemiologic features of equine Leptospira interrogans of human significance.

Leptospirosis is a zoonotic bacterial disease caused by Leptospira interrogans. There is a serologic evidence that horses are exposed to L. interrogans and, as a shedder of these organisms, can be a threat to humans. We examined risk factors associated with the risk of testing seropositive to three L. interrogans serovars (L. icterohaemorrhagiae, L. grippotyphosa, and L. canicola) in the horses of New York State, in order to understand the epidemiology of the disease and suggest strategies to control and prevent equine leptospirosis. To carry out this study, blood samples were collected from a random sample of 2551 horses and tested for the presence of antibodies to the above serovars using the microscopic agglutination test. Samples with a titer $100 were considered positive. Clinical and demographic data were collected on each horse, the farms' management practices and ecology. Logistic regression analysis was used to develop a multivariate indexing system and to identify factors significantly associated with the risk of leptospirosis. Four indices were developed based on the possible sources of exposure: rodent exposure index; wildlife exposure index; soil and water index; and management index. The soil and water index was significantly associated with the risk of exposure to all three serovars. Management was positively associated with L. icterohaemorrhagiae and L. canicola. Density of horses turned out together was positively associated with the risk of exposure to L. grippotyphosa. We concluded that indirect exposure of horses to L. interrogans through contaminated soil and water appears to be significantly associated with the risk of exposure to all three serovars. Management appears to play an important role in the exposure to L. interrogans. Modification of management practices might reduce the horses' risk of exposure and hopefully minimize the human hazards.

Incidence of leptospiral abortion in Brazilian dairy cattle.

We examined dams' paired serum samples and foetal kidneys (histopathologically and attempting leptospiral cultures) from 120 Brazilian Holstein abortions from 10 herds near Sao Paulo, Brazil, in 1996. Leptospiras was isolated from 15 foetuses. The Leptospira interrogans serovar hardjo was obtained from four, pomona from three and wolffi from eight foetuses. Ten of these 15 foetuses showed a four-fold rise in titres between the day of abortion and the second samples taken 15 days later. Fifty-seven other foetuses had histologic evidence of leptospires; 27 of their dams (47%) had four-fold rises in titres. In total, 72 of 120 aborted foetuses had evidence of leptospiral infection.

Leptospira interrogans serovar icterohaemorrhagiae seropositivity and the reproductive performance of sows.

The reproductive performance of 28 sows seropositive to Leptospira interrogans serovar icterohaemorrhagiae was compared with that of 87 Leptospira sp. seronegative dams belonging to the same herd. Sows were sampled during 1988 to 1993. During this period the herd was not submitted to any kind of intervention (antibiotic therapy, immunoprophylaxis or rodent control). Relative risks (RR) of return to heat, mummified fetuses, stillbirth, and weak newborn piglets for infected sows were assessed and the differences in means of total piglets born per litter, piglets born alive, piglets effectively housed, weaned piglets, stillbirths, mummified fetuses, weak newborn piglets, weight at birth of the piglets effectively housed, weight at 21 days of life and weight at weaning were evaluated. Seropositive dams had a greater risk of having weak newborn piglets (RR = 1.67, 1.02 < or = CI 95% < or = 2.72) and also of having more weak newborn piglets per litter (P = 0.01). Other variables examined were not different (P > 0.05).

Retinal immunopathology in horses with uveitis.

BACKGROUND: Equine uveitis is a spontaneous disorder of horses that can serve as a model for the study of human uveitis. Although the initial presentation is that of an anterior uveitis, retinal involvement has been noted in some cases. We report here the immunohistopathology of retinas from horses with uveitis. METHODS: Sections of eyes recovered from horses with naturally occurring uveitis and from Shetland ponies with experimental leptospira-induced uveitis were stained by hematoxylin and eosin for histopathological evaluation. Immunohistochemistry was used to evaluate retinas for MHC Class II antigen expression and infiltration of T and B lymphocytes. RESULTS: Histopathological abnormalities in retinas from horses with uveitis ranged from minimal to total loss of retinal tissue. MHC Class II antigen-positive round and dendritiform cells were seen in these retinas, but were not seen in retinas from horses without uveitis. There was no significant reactivity noted in the retinal pigment epithelial cells or Muller cells. Numbers of MHC Class II antigen-expressing cells and T lymphocytes correlated with the extent of retinal histopathology. B lymphocytes were seen primarily in retinas from horses that were seroreactive for Leptospira interrogans serovar pomona. Retinas from ponies with experimental uveitis had changes similar to those from horses with spontaneous uveitis. CONCLUSIONS: These results suggest that retinal pathology may be a primary immunological event in equine uveitis, provide evidence that leptospira-associated uveitis may be a distinct subset of equine uveitides, underscore the relevance of the study of equine uveitis to human uveitis, and support the plausibility of a post-infectious immunopathogenesis of some naturally occurring uveitides in both humans and horses.