Al Ridler

Prevalence of pathogenic Leptospira spp. in sheep in a sheep-only abattoir in New Zealand

Abstract AIM: To determine the prevalence of the two most commonly diagnosed pathogenic Leptospira spp. serovars, Hardjobovis and Pomona, in sheep in a sheep-only abattoir in New Zealand, and to determine the prevalence of kidneys which were leptospire culture-positive collected from sheep seropositive or seronegative to the microscopic agglutination test (MAT). METHODS: A repeated cross-sectional observational study was conducted of serological and kidney culture prevalences of Leptospira borgpetersenii serovar Hardjobovis and Leptospira interrogans serovar Pomona. Lines of sheep and individual sheep were systematically randomly selected at a sheep-only abattoir during 18 May 2004 to November 2004 and 06 December 2004 to 14June 2005. Additionally, a cross-sectional study examined prevalences in a purposively selected line of sheep from a flock with clinical evidence of an outbreak of leptospirosis. RESULTS: In the study population of 15,855 sheep of which 2,758 were sampled, 5.7 (95% CI=4.9–6.7)% were seropositive to one or both serovars; 44.2 (95% CI=34.6-54.2)% of 95 lines of sheep and 44.9 (95% CI=35.0-55.3)% of 89 farms showed serological evidence of infection. The serological prevalence of serovar Hardjobovis was significantly higher than that of serovar Pomona both at line (33% and 4%, respectively) and individual (5% and 1%, respectively) levels. A low but persistent seroprevalence of Hardjobovis throughout both years suggested low-level endemicity to this serovar, whereas Pomona infections appeared to besporadic. Leptospires were isolated from kidneys of 8/37 (22%)Hardjobovis- and 1/6 (17%) Pomona-seropositive, and 5/499(1%) seronegative animals. Of the animals purposively sampled from a farm with a clinical outbreak of leptospirosis, all kidneys from the 13 seropositive animals were culture-positive, indicating a high risk of exposure of meat workers in outbreak situations. Kidneys of MAT-seropositive sheep were 21.7 (95% CI=7.6–61.9) times more likely to test culture-positive than kidneys from animals with negative MAT titres. In general, the results indicated that 13/1,000 sheep slaughtered were potentially shedding leptospires. CONCLUSIONS: The study demonstrated the presence of a definite risk of occupational exposure of meat workers in a sheep-only slaughterhouse to the two most commonly diagnosed pathogenic Leptospira spp. serovars in New Zealand.

Assessment and simulation of the implementation of brucellosis control programme in an endemic area of the Middle East

Brucellosis is an important zoonosis in Middle Eastern countries. In this study we assessed the extent of the application of planned official brucellosis control programmes in Kafr El Sheikh governorate, Egypt and we used a stochastic simulation model to assess the probable impact of changes to the official control strategy on the dynamics of small-ruminant brucellosis. Our results show that <7% of female livestock were tested in any given year in the study area and that quarantine was not consistently applied to infected herds. Simulation results revealed the inability of the applied control measures to reduce the prevalence of small-ruminant brucellosis. Given our assumptions, the intensity with which infected animals are removed under the actual levels of implementation of test-and-slaughter programmes would permit brucellosis to remain endemic at a level >8% of the sheep and goat population.

Ruminant brucellosis in the Kafr El Sheikh Governorate of the Nile Delta, Egypt: prevalence of a neglected zoonosis.

Background Brucellosis is a neglected tropical zoonosis allegedly reemerging in Middle Eastern countries. Infected ruminants are the primary source of human infection; consequently, estimates of the frequency of ruminant brucellosis are useful elements for building effective control strategies. Unfortunately, these estimates are lacking in most Middle East countries including Egypt. Our objectives are to estimate the frequency of ruminant brucellosis and to describe its spatial distribution in Kafr El Sheikh Governorate, Nile Delta, Egypt. Methodology/Principal Findings We conducted a cross-sectional study in which 791 sheep, 383 goats, 188 cattle milk tanks and 173 buffalo milk tanks were randomly selected in 40 villages and tested for the presence of antibodies against Brucella spp. The seroprevalence among different species was estimated and visualized using choropleth maps. A spatial scanning method was used to identify areas with significantly higher proportions of seropositive flocks and milk tanks. We estimated that 12.2% of sheep and 11.3% of goats in the study area were seropositive against Brucella spp. and that 12.2% and 12% of cattle and buffalo milk tanks had antibodies against Brucella spp. The southern part of the governorate had the highest seroprevalence with significant spatial clustering of seropositive flocks in the proximity of its capital and around the main animal markets. Conclusions/ Significance Our study revealed that brucellosis is endemic at high levels in all ruminant species in the study area and questions the efficacy of the control measures in place. The high intensity of infection transmission among ruminants combined with high livestock and human density and widespread marketing of unpasteurized milk and dairy products may explain why Egypt has one of the highest rates of human brucellosis worldwide. An effective integrated human-animal brucellosis control strategy is urgently needed. If resources are not sufficient for nationwide implementation, high-risk areas could be prioritized.

Assessment of occupational exposure to leptospirosis in a sheep-only abattoir.

This study estimated the frequency of exposure of meat workers to carcasses infected with Leptospira serovars Hardjobovis or Pomona in a sheep-only abattoir in New Zealand. A stochastic spreadsheet model was developed to assess the daily risk of exposure of eviscerators, meat inspectors and offal handlers to live leptospires in sheep carcasses from May to November 2004 (high-risk period), and from December 2004 to June 2005 (low-risk period). The average sheep processed per day were 225 for an eviscerator, 374 for a meat inspector, and 1123 for an offal handler. The median daily exposures during high- and low-risk periods were 11 [95% distribution interval (DI) 5-19] and three (95% DI 1-8) infected carcasses/day for eviscerators, 18 (95% DI 9-29) and six (95% DI 2-12) for meat inspectors, and 54 (95% DI 32-83) and 18 (95% DI 8-31) for offal handlers, respectively. Stochastic risk modelling provided evidence that processing of sheep carcasses exposed meat workers regularly to live leptospires with substantial seasonal variation.

Prevalence of Neospora antibodies in beef cattle in New Zealand

Abstract dAim:To estimate the prevalence of Neospora infection in a sample of New Zealand beef cattle. dMethods: The prevalence of Neospora caninum infection in New Zealand beef cattle was estimated by collecting blood at slaughter from 499 beef cattle from 40 different farms at 2 slaughter plants in the North Island and 1 in the lower South Island. Sera were tested using an ELISA against Neospora tachyzoite antigen. dResults: The prevalence of seropositive cattle was 2.5% (n=120), 3.6% (n=166) and 2.3% (n=213) at the plants surveyed, the overall prevalence being 2.8%. The serologically positive cattle came from 9 farms, 3 of which had more than 1 positive animal. The highest prevalence recorded amongst animals from 1 farm was 4/13 (31%), in a group of young steers. dConclusion: Neosporosis appears to be present at a lower level in the New Zealand beef cattle population than in the New Zealand dairy cattle population. Nevertheless, from the high seroprevalence evident amongst young cattle on 1 farm, we suggest that Neospora may be a cause of infertility in beef cattle in this country.

Control of Brucella ovis Infection in Sheep

Approach to control of Brucella ovis would vary in different countries and areas depending on farm and flock characteristics and economic factors. Eradication by a test-and-slaughter approach is the most desirable option in areas where it is logistically and financially feasible. Vaccination is used in areas with a high incidence of infection where eradication would be difficult. Voluntary accreditation programs have been established in some countries and are of particular benefit to pedigree ram breeders.

Transmission of Brucella ovis from rams to red deer stags.

Abstract Aim: To determine whether B. ovis will transmit from infected rams to non-infected red deer stags (Cervus elaphus) grazing together in the same paddock. Methods: Six rams artificially infected with B. ovis were grazed with six non-infected 14-month-old red deer stags for a four and a half month period from March 4 to July 20, 1999. Stags were blood sampled at one- to six- weekly intervals to test for B. ovis antibodies using a complement fixation test. Stags that seroconverted were semen sampled to test for B. ovis infection by bacteriological culture. Results: Between day 92 and day 124 of grazing together (June 4 and July 6), sera from five of the six stags became positive in the B. ovis complement fixation test. B. ovis was cultured from semen samples from four of the seropositive stags. Conclusions: Brucella ovis can be transmitted from infected rams to non-infected stags grazing in the same paddock, suggesting that B. ovis infection in farmed deer in New Zealand initially came from infected rams.Whether transmission occurs from direct contact between rams or stags, or indirectly by environmental contamination needs to be established.

Preliminary evaluation of the effectiveness of captive-bolt guns as a killing method without exsanguination for horned and unhorned sheep

The current study aims to make welfare-based recommendations for gun/cartridge combinations and shooting positions that will ensure death of the sheep (horned, unhorned, rams and ewes), without the need for either sticking or pithing. The study examined the pathophysiology of captive-bolt gun (CBG) injuries that result in incomplete concussion leading to death. Behavioural, brainstem and cranial/spinal responses were examined along with gross pathology in 489 animals (116 polled ewes, 134 horned ewes, 117 polled rams and 122 horned rams) following a variety of CBG-cartridge combinations. Shooting horned rams was more challenging than unhorned sheep, partly because minor movements of the head at the time of shooting can result in deflection of the gun by the horns. Marksmanship was the definitive factor: 100% of animals that showed signs of incomplete concussion were found to have been shot incorrectly. The findings will have application when it is necessary to kill sheep on farms for disease control or euthanasia purposes.

Ruminant brucellosis in Upper Egypt (2005–2008)

Brucellosis is endemic among humans and ruminant in Egypt and recent reports suggest that its incidence may be increasing. In this study we describe the frequency of brucellosis among different ruminant species in Upper Egypt and its spatial distribution using the data generated by a large-scale control campaign undertaken between 2005 and 2008. A total of 120,090 individual animals of different ruminant species were tested during the campaign. The true proportions of brucellosis were estimated as 0.79% (CI: 0.71%-0.87%), 0.13% (CI: 0.08%-0.18%), 1.16% (1.05%-1.27%) and 0.44% (0.34%-0.54%) among cattle, buffaloes, sheep and goats respectively. We estimated that 0.2% (CI: 0.16%-0.23%) of households in the study area keep at least one seropositive animal. Spatial autocorrelation of the proportions of seropositive households and seropositive animals was assessed using Global Univariate Morans I and Local Univariate LISA. These analyses showed that the distribution of seropositive animals has considerable spatial heterogeneity with clustering in the northern governorates of the study area. Our results show that brucellosis is widespread and heterogeneously distributed in Upper Egypt. At the current level of available resources it is very unlikely that test and slaughter could be implemented with the intensity needed to be effective and other control measures that could replace or complement the test and slaughter policy in place should be considered. Also, this study illustrates some of the challenges faced by bilateral projects that have to accommodate an externally funded intervention with an ongoing national official disease control program.

Effects of body condition score and nutrition in lactation on twin-bearing ewe and lamb performance to weaning

This study investigated the effect of feeding and body condition during late pregnancy and lactation on both ewe and lamb performance until weaning. On day 141 of pregnancy, ewes with a body condition score (BCS) of 2.0, 2.5 or 3.0 were allocated a ‘Low’, ‘Intermediate’ or ‘High’ feeding treatment until weaning at day 79 of lactation. Feeding treatments had no effect on lamb live weight at birth, summit metabolic rate or indices of colostrum intake (P > 0.05). At weaning, lambs born to the High treatment were heavier than the Intermediate treatment, which were heavier than the Low treatment (P < 0.05). Lambs reared by ewes with a BCS of 2.0 were lighter during the lactation period than lambs whose dam had a BCS of 2.5 or 3.0 (P < 0.05). In addition, lambs reared by ewes with a BCS of 2.0 had greater summit metabolic rates and greater survival to weaning than those reared by BCS 3.0 (P < 0.05) but not BCS 2.5 (P > 0.05). There was, however, no effect of feeding treatment on lamb survival to weaning. These results indicate that, within these BCS, benefits could be gained from greater BCS in late pregnancy across all feeding treatments.