The epidemiology of Leptospira interrogans serovar pomona in grower pig herds

An epidemiological study on four farms showed that leptospiral infection became apparent in piglets from 12 weeks of age. The intensity of leptospiruria was greatest in the first 3-4 weeks of infection and from then on declined and became intermittent. Factors affecting the cultural and serological prevalence of infection of the piglets were found to be the standard of hygiene and variations in the titre of the dam. Dams with high titres gave better protection to their young than did those with low titres. The spread of infection within piggeries was encouraged by mixing infected with uninfected pigs, which resulted in epidemics within the pens. Transmission from infected to susceptible grower pigs continuously occurred in grower houses, with a constant proportion of pigs becoming infected each week.     

A Serological Survey of Leptospira interrogans serotype pomona in Saskatchewan Horses

Leptospira interrogans serotype pomona antibody titres of 1:100 or greater were detected in 12.8% of 408 adult horses from seven of eight sampled herds in Saskatchewan. The geographical distribution of the seropositive horses was widespread throughout the agricultural area of the province. The geographical distribution and the cumulative increase in prevalence with age suggested that serotype pomona is enzootic in the equine population of Saskatchewan.     

Prevention of Leptospira interrogans serovar pomona infection in cattle

A commercial hardjo-pomona vaccine which has previously been shown to be effective against hardjo infection was tested against pomona. Following challenge all 11 six-month-old non-vaccinated calves seroconverted and pomona was isolated from blood or urine on at least one occasion from nine of them. Pomona was isolated once only, on the third day after challenge, from the blood of one of 11 vaccinated calves.     

Monoclonal antibodies to Leptospira interrogans serovar pomona.

Three monoclonal antibodies produced against Leptospira interrogans serovar pomona have been studied for their diagnostic usefulness. All three monoclonals reacted strongly in the enzyme-linked immunosorbent assay and indirect fluorescent antibody test with serovar pomona and did not react with serovars grippotyphosa, canicola, icterohaemorrhagiae and hardjo.     

Leptospira interrogans serotype pomona infection in pigs: prevention of leptospiruria by immunisation before exposure to a natural infection

Fourteen of 24 pigs were immunised with repeated injections of killed cultures of Leptospira serotype pomona administered over a three-week period. The remaining 10 pigs served as controls.

Five days after immunisation all pigs were exposed to the same natural infection by being housed together for 12 weeks in a pen which received effluent from other pens containing infected pigs.

Neither leptospiruria nor kidney lesions were detected in any of the immunised pigs. In contrast, leptospiruria and kidney lesions occurred in all the controls.

The development of serum agglutinins after immunisation and before exposure suggested that this could be used as an index of adequate antigenic stimulation.     

Observations on three outbreaks of Leptospira interrogans serovar pomona infection in lambs

Sickness and deaths associated with leptospirosis were reported in three lamb flocks in the Manawatu region. The clinical, pathological and serological features of Leptospiru interrogans serovar pomona infection are described. The mucous membranes of affected animals were pale and jaundiced. Haemoglobinuria, haemoglobinaemia and centrilobular hepatocellular necrosis were also consistent findings. All clinically sick lambs had very high titres in the microscopic agglutination test for L. pomona. Circumstantial evidence of pigs being the source of infection was found in one of the three cases.     

Viability of Leptospira interrogans serotype grippotyphosa in swine urine and blood.

Normal swine urine, devoid of its microbial flora, diminished the viability and virulence of Leptospira interrogans serotype grippotyphosa. Bovine serum albumin diluent effectively offset the urine's deleterious effects. Membrane filtration (0.45 micrometer) rendered urine free of bacteria, but permitted passage of limited numbers of leptospires. Most of the commonly used anticoagulants did not alter viability of grippotyphosa in whole blood. However, EDTA significantly reduced the number of viable cells.     

Experimental infection of calves with Leptospira interrogans serotype szwajizak

This is a report on the experimental infection of cattle with Leptospira interrogans serotype szwajizak. The principal clinical features in three 4-week-old Holstein-Friesian heifers intravenously inoculated were fever, listlessness, anorexia, weakness, and diarrhea. Szwajizak was isolated from the blood for the first 5 to 8 days after inoculation. Leptospires were recovered from kidneys, but not from liver, spleen, brain, or urine. Two of the 3 calves produced homologous agglutinins, with maximum serum titers of 1:80 and 1:160. The sera of the 2 calves that developed szwajizak agglutinins showed cross reactivity with wolffi and hardjo antigens. There were not significant differences of plasma and urine constituents between the inoculated calves and the control calf. Endocardial hemorrhages and large soft black-red spleen were present in the 2 calves given the greatest numbers of leptospires. Histopathologically, kidney of all infected calves had multiple small foci of lymphoid cells, chiefly pasmacytes, which were present in periglomerular and interstitial areas.     

Experimental infection of lactating goats with Leptospira interrogans serovars pomona and hardjo

Pathogenesis of Leptospira interrogans serovars pomona and hardjo was evaluated in 14 lactating goats. Although mild clinical signs of leptospiral infection characterized by pyrexia and reduction in milk yield appeared in some animals, a consistent clinical pattern was not observed in the inoculated animals. The pomona serovar was isolated from the kidney of 1 of the 4 goats inoculated with serovar pomona. The hardjo serovar (strain UI 750) was isolated in the rabbit serum-supplemented bovine albumin polysorbate-80 liquid medium only from the mammary gland of 1 of 4 goats at 13 days after inoculation with serovar hardjo. The positive culture was detected after an 8-month incubation period.     

Enzymatic radioimmunoassay for detecting Leptospira interrogans serovar pomona in the urine of experimentally-infected pigs

An enzymatic radioimmunoassay (ERIA) has been developed for detecting Leptospira interrogans serovar pomona in porcine urine. Four grower pigs were experimentally infected with serovar pomona. A total of 39 urine samples was collected, and ERIA was compared with dark ground microscopy (DGM) and culture for demonstrating leptospiruria. Of 20 samples positive by at least one technique, leptospires were detected by ERIA in 14, by culture in 16 and by DGM in 13. ERIA, unlike the other 2 methods, was suitable for use with urine which had been stored frozen for several months.     

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.     

Isolation of Leptospira interrogans serovars tarassovi and pomona from dogs

Extract

This communication reports the isolation of Leptospira inter-rogans serovars tarassovi and pomona from dogs in New Zealand.