Leptospirosis outbreak in a piggery in southern alberta

Fourteen abortions, stillbirths and neonatal deaths occurred over an interval of one month in crated sows in a farrow-to-finish swine operation. Leptospira interrogans serovar pomona (kennewicki by DNA analysis) was demonstrated by culture and fluorescent antibody test to be present in sows, piglets, boars, feeders, drinking water and skunks on the premises.

Antibody was found in all clinically affected sows, at serum dilutions ranging from 1/800 to 1/25,600, and in all breeding boars at titers from 1/50 to 1/1600. Pomona antibody was present in 118 sow sera collected nine months before the outbreak, at a prevalence of 21.3%. Parvovirus infection in fetuses was intercurrent with the leptospirosis epizootic, despite vaccination for the former. Environmental contamination, feedback through skunks via drinking water, and dissemination through the piggery are discussed.

     

Leptospirosis: II. Investigation of clinical disease in dairy cattle in the Waikato district of New Zealand

Investigations were carried out in 1975, 1976 and 1977 in 16 dairy herds where leptospiral abortions were suspected and in five other herds where clinical disease was not present. Both Leptospira interrogans serovars pomona and hardjo were isolated from cattle in herds with leptospirosis, but only pomona was recovered from those that had aborted. There was no evidence that hardjo caused clinical disease in dairy cattle in the Waikato district.

It was found that 73% of the cows that aborted and 19% of other animals in the same herds had microscopic agglutination test titres to pomona of 1:2 000 or greater. By contrast, only 2% of cattle in herds without clinical evidence of leptospirosis had such titres. One cow retained a titre of 1:2 000 or greater to pomona for 7 months; titres of this order had a shorter duration in other cows. Leptospiruria occurred in 50% of cows that had aborted and in 9% of in-contact cows in the same herds. Only 0.7% of cows had leptospiruria in the herds with no clinical disease. Ten of 35 cows shedding pomona still had leptospiruria one month later.

It was concluded that clinical leptospirosis should be diagnosed by testing a sample of the herd, rather than just individual cows, because of the variability and persistence of leptospiruria and serological titres in cows with and without clinical signs. Although hardjo is common in cattle in the Waikato district, it was not found to cause abortion in cattle.     

Haemolytic disease associated with Leptospira Interrogans serovar pomona in red deer calves (Cervus elaphus)

Three red deer calves (Cervus elaphus) died with a haemolytic disease associated with infection by Leptospira interrogans serovar pomona.

Infection within the herd was more prevalent than disease. Sera from 16 herd mates were tested by the microscopic agglutination test (MAT) and 12 had leptospiral titres, the majority to serovar pomona. A few calves had titres to balcanica and hardjo.

Urine was obtained for culture from six of these calves and serovar pomona was isolated from five with titres to pomona, and hardjo from one with a litre to hardjo but not pomona.

A fourth calf died with severe nephritis but a diagnosis of leptospirosis was not confirmed in this case.     

Leptospirosis: I. Clinical investigation of the infection in dairy cattle in the Waikato district of New Zealand

An investigation was made into the prevalence of leptospiral infection in cattle. An area 50 km radius was selected in a region where leptospirosis was reputedly common. Farmers volunteered 250 herds with 39 500 cows for testing and 7 500 animals were selected and sampled. Twenty-nine cows (0.4%) on 14 (5.6%) of the farms had leptospiruria at the first examination. Leptospirae were cultured from the urines of nine of these animals and all were Leptospira interrogans serovar hardjo. Serologically 12.5% of cows had titres of 1:200 or greater to hardjo and 3.5% titres of 1:200 or greater to pomona. In the Spring of 1977, there was evidence of clinical leptospirosis in calves associated with only one of the herds and no clinical leptospirosis in the 250 lactating herds, although leptospiral titres were found in 88% of them. This indicated that clinical disease was much less common than infection. We concluded that leptospirosis was of minor economic importance in dairy cattle, although it could be significant in individual herds, and a health hazard to farm workers.     

Isolation and Identification of a Leptospire of The Hebdomadis Serogroup (L. Hardjo) From Cattle in Canada

During the summer of 1961 an outbreak of atypical mastitis in a small herd of dairy cattle was investigated. The clinical findings, which included a single abortion, were suggestive of leptospirosis and serological studies indicated that a serotype other than the usual L. pomona was the causative agent. A fastidious leptospire recovered from the urine of one cow has been identified as L. hardjo, a member of the hebdomadis group. The difficulties encountered in isolation, adaptation to standard media and serotyping are described.     

Phage typing of staphylococci isolated from dairy cows in New Zealand

Four red deer calves (Cervus elaphus) died with severe nephritis apparently associated with infection by Leptospira interrogans serovar pomona. The sera of 12 in-contact red deer calves were examined for leptospiral agglutinins and nine showed titres to pomona consistent with recent infection. Two also showed titres of 1:100 to serovar hardjo. The urine of five of these in-contact calves was examined periodically over a period of nine months. All were initially leptospiruric, four being infected with pomona and one with hardjo. In four animals leptospiruria could only be detected for up to six months, but one animal infected with pomona was leptospiruric for at least eight months.

The apparent source of infection was from infected cattle, and it is suggested that deer are unlikely to act as maintenance hosts for serovar pomona.     

Protection of pregnant swine by vaccination against leptospira infection

SUMMARY The protection conferred on pregnant gilts by 2 commercially available Leptospira interrogans serovars pomona and tarassovi bacterins was evaluated. Gilts vaccinated either 3, 6 or 12 months prior to natural challenge with L. interrogans serovar pomona had significantly lower abortion rates (2% vs 69%) and foetal mortality rates (14% vs 57%) than unvaccinated controls. One vaccine was significantly superior to the other and contained approximately twice the number of L. interrogans serovar pomona organisms per vaccine dose. Neither vaccine protected against renal colonisation but vaccination reduced urinary excretion of leptospires. Both vaccines reduced agglutinating antibody response to infection, as measured by the microscopic agglutination (MA) test. This may prevent the detection of a carrier animal by serology. Foetal pigs did not develop specific MA titres. Cultural methods were not reliable in making a diagnosis of foetal infection. Histopathology of foetal liver and kidneys helped in making a diagnosis of foetal infection.     

Hypomagnesaemia in cattle

Leptospirosis is an important animal and human health problem in New Zealand, and the epidemiological and ecological aspects of infection in domestic species and free-living species are described. The characteristics of infection with a particular serovar are often considerably different in different species of animal and primary epidemiological investigations involve differentiating between maintenance-host populations and accidental-host populations for the serovars present in a particular ecosystem.

Cattle and pigs are maintenance hosts for hardjo and pomona respectively. Balcanica is maintained by possums (Trichosurus vulpecula) and ballum is maintained by the house mouse (Mus musculus), ship rat (Rattus rattus) and hedgehog (Erinaceus europaeus). In some regions, foci of copenhageni infection are maintained by Norway rats (Rattus norvegicus). Each serovar shows a high degree of parasitic adaption to its maintenance-host species and this is reflected in the nidality of leptospirosis in intensive farming environments. Accidental infections in domestic animals and man are the consequence of ecological associations with maintenance-host populations for particular serovars.

Control of leptospirosis in domestic animals depends on decreasing the prevalence of infection with serovars maintained within populations of domestic animals, and decreasing the degree of ecological association with free-living maintenance-host populations. Vaccination of cattle against hardjo. will considerably reduce the prevalence of infection in vaccinated herds and therefore decrease the prevalence of accidental hardjo infections in man.     

Correlation of Bedrock Type with the Geography of Leptospirosis

Leptospirosis occurs enzootically over most of Southern Ontario. Leptospira pomona is the serotype most commonly found in outbreaks. Antibodies to L. pomona occur frequently in the sera of deer in wilderness areas. The geographic location of leptospirosis presents a pattern which closely parallels the distribution of Paleozoic bedrock. By contrast, L. pomona infection is absent from areas underlain by Precambrian bedrock. Comparisons of water chemistry, soil type, habitat, and host and pathogen availability in these two geologically distinct environments have not defined the mechanisms involved in the disease pattern. Leptospires resembling saphophytic strains occur widely, regardless of bedrock type. High titers to L. biflexa, a saprophytic serotype, were found frequently in deer sera from a Precambrian area which was surveyed intensively. Antibodies to L. hardjo and L. sejroe occur in many bovine sera from a predominantly Precambrian area where Paleozoic outliers are numerous. Colloidal clay is common to leptospiral habitats. A microenvironment structured by the surface activity of clay is likely to be a key ecological factor in the landscape epizootiology of leptospirosis. In Ontario, bedrock composed of limestone and dolomite formed in the Paleozoic era appears to be a reliable ecological marker for Leptospira pomona infection.     

Leptospirosis in Colombia: Isolation ofLeptospira SPP. from the kidneys of brown rats (Rattus Norvegicus) trapped on infected piggeries

Summary Leptospira interrogansserotypes pomonaand icterohaemorrhagiaewere isolated from the kidneys of Rattus norvegicustrapped on pomonainfected piggeries.The isolation of pomonafrom one of 111cultured kidneys, although of interest, strongly suggests that this rat does not play an important part in the epidemiology of infection by this serotype. Kidney tubular degeneration, focal mononuclear infiltrations and fibroplasia are morphological traces which remain after an attack of leptospirosis. The high percentage (48.6)of these lesions found in the rat kidneys examined does not seem to be related to serotype pomonabut to icterohaemorrhagiae.The importance of this last serotype in swine in the Cauca Valley has yet to be assessed.

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Leptospirosis En Colombia: Aislamiento DeLeptospira SPP. De Riñones De Ratas Pardas (Rattus Norvegicus) Atrapadas En Porquerizas Infectadas

Resumen Se aislóLeptospira interrogans serotipospomona eicterohaemorrhagiae de riñones deRattus norvegicus atrapadas en porquerizas infectadas porpomona. El aislamiento depomona de 1/111 riñones cultivados, aunque de interés, sugiere que esta rata no desempeña parte importante en la epidemiología de las infecciones por este serotipo.Degeneración tubular renal, infiltración mononuclear focal y fibroplasia son huellas morfológicas que quedan después de un ataque de leptospirosis. El alto porcentaje (48.6) de estas lesiones encontradas en los riñones de las ratas examinadas no parece estar relacionado con el serotipopomona sino con elicterohaemorrhagiae. La importancia de este último seroptipo en cerdos en el Valle del Cauca no se ha evaluado todavía.

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Leptospiroses En Colombie: Isolement DeLeptospira SPP. De Reins De Rats Bruns (Rattus Norvegicus) Captures Dans Des Porcheries

Résumé Les sérotypespomona eticterohaemorrhagiae deLeptospira interrogans ont été isolés de reins deRattus norvegicus capturés dans des porcheries infectées de (pomona?). L'isolement depomona sur une seule des 111 cultures de rein effectuées, bien qu'interessant, suggère fortement que ce rat ne joue pas un rôle important dans l'épidémiologie de l'infection par ce sérotype.La dégénerescence tubulaire des reins, des infiltrations ponctuelles par des monocucléaires et l'aspect fibreux constituent les traces morphologiques qui demeurent après une attaque de leptospirose. Le pourcentage élevé (48,6) de ces lésions trouvées dans les les reins des rats examinés semble être plus en rapport avec le sérotypeicterohaemorrhagiae qu'avec le sérotypepomona. L'importance du sérotypeicterohaemorrhagiae chez le porc de la Cauca Valley est encore à vérifier.

     

RENAL LEPTOSPIROSIS IN VACCINATED PIGS

SUMMARY The ability of 2 commercial leptospirosis vaccines to prevent renal colonisation with Leptospira interrogans serovar pomona was studied in pigs. Based on bacteriological, pathological and serological findings some degree of protection was found in vaccinates when compared with non-vaccinates after challenge 4, 7 and 12 months after vaccination. However, the degree of protection was insufficient to prevent colonisation and renal leptospirosis in 6 of 10 pigs at 4 months, 7 of 10 pigs at 7 months and 8 of 10 pigs at 12 months.     

Some Observations on the Diagnosis and Epidemiology of Leptospirosis in Swine

The results of combined epidemiological, clinical, serological, bacteriological and histopathological studies following an outbreak of disease caused by L. pomona on a farm stocked with cattle, sheep, pigs, goats and horses maintained for experimental purposes, are reported.

The incidence of infection was high in horses, cattle and pigs. A few low titres were seen in sheep. The goats were not infected. Apart from a single bovine abortion all the clinical symptoms observed occurred in pregnant sows. Seven of these aborted or gave birth to stillborn pigs within a six week period.

Fifteen species of wildlife were trapped or shot on the farm during the year following the outbreak. L. pomona was isolated from four skunks and a porcupine. Epidemiological studies indicated that wildlife reservoir hosts were the primary source of infection for the domestic livestock.

Leptospiruria and the serological response were studied in a group of eight infected sows. Microscopic agglutination titres of 10² or less could not be associated with leptospiruria and the duration of leptospiruria was found to range from a few weeks to over two years in individual sows. Direct dark-field examination of urine proved superior to guinea-pig inoculation as a method of detecting leptospiruria and it is suggested that the former technique could be adopted with advantage as a routine aid to diagnosis.

     

Leptospirosis: An important infectious disease in North American horses

North American horses are commonly exposed to Leptospira organisms. Leptospira Bratislava is the most common infecting serovar but this serovar has not been confirmed to cause clinical disease in North American horses. Leptospira Pomona type kennewicki is responsible for most of the clinical diseases (leptospirosis) in North American horses. Leptospirosis is most commonly associated with diseases of the placenta and fetus, the kidneys and the eyes in horses. In-utero infections in pregnant mares may result in abortion, neonatal illness or birth of an antibody positive healthy foal. Acute renal failure in younger horses and recurrent uveitis in adult horses are other well documented clinical syndromes of leptospirosis. Abortions, neonatal disease and acute renal failure are caused by a subacute infection, while horses with Leptospira associated recurrent uveitis develop ocular disease months or years after the initial Leptospira infection. Diagnosis of Leptospirosis is made by a combination of antigen or antibody testing methods. Mares that abort following Leptospira infection have no additional clinical signs at the time of abortion but may shed the offending Leptospira spp. in the urine for several weeks. Antibiotic treatments are sometimes used in hopes of decreasing Leptospira shedding in infected horses or prophylactically in exposed pregnant mares but documentation of efficacy is lacking. Horses with Leptospira - associated acute renal failure can be successfully treated with antibiotics and supportive care. Recurrent uveitis is commonly associated with leptospirosis in North American horses and although horses may have chronic intraocular infection triggering an immune disease, systemic antimicrobial therapy has not been effective in eliminating the organism from the eye. An equine approved Leptospira Pomona type kennewicki vaccine is now available in North America.     

Epidemiology of leptospirosis in dairy farm workers in the Manawatu. Part II. A case-control study of high and low risk farms

Subsequent to a cross-sectional serological survey of Manawatu dairy farm workers, a case-control study was carried out to investigate the correlation between titres to leptospiral serovars in workers and those in cattle in their herds. A total of 52 herds was investigated, 25 of which were ‘high risk’ where milkers had titres of 1:96 or greater, and 27 were case-controls where milkers had no detectable agglutinin titres at a minimum serum dilution of 1:24.

The serological prevalence of titres to hardjo in cattle on ‘high risk’ farms (76.5%) was significantly higher (P<0.05) than on the case-control farms (60.0%). The geometric mean titres of seropositive cattle on ‘high risk’ farms were also significantly higher (P<0.0l) than in the cattle from the case-control farms, especially in the younger cohorts. These findings suggest that there was active endemic hardjo infection in the two- to three-year-old cattle on the ‘high risk’ farms.

Titres to pomona were demonstrated in only 5.2% of the cattle from both types of farm. Workers with titres to pomona tended to be from farms on which stock, especially calves, were bought-in and pigs were kept.

Conventional measures for protecting milkers from contact with infected urine appeared to be ineffective and it is concluded that prevention of leptospirosis in dairy farm workers can only be achieved by elimination of infection in the herd by vaccination of cattle.     

Experimental infection of neonatal pigs with CNF toxin-producing strains of Escherichia coli

To examine and compare the pathogenicity of cytotoxic necrotising factor (CNF)-producing Escherichia coli, two litters of piglets were infected orally with 10¹⁰E coli O88 or 10¹⁰E coli O32 strains. Of the six piglets infected with E coli O88, two died within 24 hours and three developed blood-stained diarrhoea. The other piglets were killed one, five, six and eight days after infection, when bacterial cultures indicated an overwhelming bacteraemic infection with E coli O88 in the early stages followed by clearance through the large intestine. The pathological changes consisted of an early enteritis, progressing to enterocolitis and a bacteraemic spread to the lungs. The histopathological changes were characteristic of toxaemic effects in brain, heart, liver and kidney, and characterised by congestion, oedema and exudation. Infection with E coli O32 produced a milder but similar enterocolitis, also with bacterial colonisation in the lungs. The histopathological findings again reflected a toxaemia. The enteritis was more persistent after E coli O32 infection and the strain persisted in large numbers in the intestine. No evidence of bacterial adherence to the intestinal mucosa was found with either strain. Enteroinvasion was only evident in one E coli O884-nfected piglet, but the consistent occurrence of interstitial pneumonia showed the predilection of these organisms for the lung. The results confirm the toxigenic properties of CNF⁺E coli and suggest an important role for this organism in enteric infection of young pigs.     

Interpretation of findings leptospirosis

Extract

Sir,—In his criticism of our recent paper in which we claimed to have demonstrated experimental leptospirosis in 19 of the 20 control calves, W. M. Webster claims that the evidence for infection in five of the control calves is unconvincing (“Standards in Scientific Contributions”, N.Z. vel. J., 6: 27). His main reasons for this opinion appear to be, first, because no significant agglutination-lysis titres were demonstrated in these calves and, secondly, the observed onset of leptospimria in three of them was later than nsnal. He further suggests that mistaken diagnosis of leptospirosis, due either to dark-ground examination of urine or to inadvertent infection in guinea pigs inoculated with calf kidney tissue, is a more probable explanation.     

Clinical and biochemical changes in sheep inoculated with leptospira interrogans serotype pomona

Clinical and biochemical changes occurring in whole blood, urine, plasma and serum of sheep experimentally infected with Leptospira interrogans serotype pomona were studied.

Half-time and fractional clearance rates of sulphobromophthalein, phenosulphophthalein and chromium (^5lCr) EDTA were also measured to assess functional damage to the liverand kidney.

The results suggested that the biochemical changes occurring following pomona infection were due mainly to haemolysis of erythrocytes and to mild impairment of tubular and glomerular kidney function. No alteration in liver function was observed: Analyses of isocitrate dehydrogenase, arginase, and total bilirubin in serum and measurements of kidney glomerular and tubular function appeared to be the most useful biochemical indicators of pomona infection in sheep.     

An unusual serological response in cattle after use of a commercial leptospiral combined hardjo-pomona vaccine

Vaccination of four calves with Leptavoid (Wellcome New Zealand Limited) gave rise to Leptospira interrogans serovars hardjo and pomona microscopic agglutination test titres that could not be distinguished in magnitude from post-infection titres. Vaccination of four calves with Lepto-3 (ICI Tasman Limited) gave rise to much lower titres.

Revaccination of cows with Leptavoid caused a rise in hardjo titres which was significantly greater than after use of Lepto-3.

The possibility that titres were due to the simultaneous infection with serovars pomona and hardjo of only the animals vaccinated with Leptavoid must he discounted.     

Is canine leptospirosis underdiagnosed in southern Ontario? A case report and serological survey

An eight-year-old city-dwelling Cairn Terrier was presented to a veterinary hospital in acute renal failure with evidence of hepatic insufficiency. The dog was treated symptomatically over three days, during which time vomiting was largely controlled, but it became jaundiced as hepatic insufficiency worsened. Leptospira pomona was demonstrated in large numbers by immunofluorescent staining of urinary sediment. It was isolated and its identity confirmed as L. pomona genotype kennewicki. The source of the infection was thought to be raccoons.

Sera from 474 blood samples submitted for diagnostic purposes to two clinical pathology laboratories in southern Ontario were examined with the microscopic agglutination test for antibodies to selected leptospiral serovars. Of the sera tested, 39.2% reacted at titers ≥1:100 with one or more serovars, the majority of all sera (26.2%) reacting at low titers to canicola or icterohaemorrhagiae, or both. These reactions likely resulted from vaccination. A smaller proportion reacted to other serovars tested: autumnalis (3.8%), bratislava (8.2%), grippotyphosa (1.9%), hardjo (3.0%), and pomona (3.2%). Among dogs reacting to these latter serovars (other than bratislava), many had broadly cross-reacting and relatively high titers. One dog with a titer of 1:800 to pomona had had a disease typical of leptospirosis two years previously. Three other dogs with high titers to autumnalis, bratislava, or mixed serovars had clinical histories compatible with leptospirosis.

We suggest that leptospiral bacterins for dogs in Ontario be broadened to include at least serovars autumnalis and pomona.

     

Three case studies involving Leptospira interrogans serovar pomona infection in mixed farming units

Three case studies involving Leptospira interrogans serovar pomona outbreaks within mixed farming systems in South Africa are described. On 2 farms, pigs constituted the main enterprise with cattle and sheep of secondary importance. On each of these 2 farms, abortion due to L. pomona in sows was confirmed by culture, and antibody titres to pomona were detected in cattle, sheep, horses and dogs. On the 3rd farm, a piggery was of secondary importance to cattle farming. Abortion and death in cows occurred on this farm and serology showed titres to various serovars, including pomona. L. pomona was also isolated from bovine urine, an aborted bovine foetus and kidneys from slaughtered pigs. This particular case study was regarded as clinically atypical in that adult Jersey cattle died of acute leptospirosis in a semiarid region of South Africa. In all 3 case studies, the poor management of pig effluent and of the drinking water and its sources played a pivotal role in the transmission of the disease. Inadequate vaccination of animals against Leptospira and poor record-keeping within the secondary farming enterprises were also contributing factors to the spread of leptospirosis.