Review: Bovine foetal mortality - risk factors, causes, immune responses and immuno-prophylaxis

This review of bovine foetal mortality (>42 d gestation) concluded that while the majority of risk factors associated with sporadic loss operate at animal-level, e.g. foetal plurality, those that operate at herd-level, e.g. some foetopathogenic infections, are more likely to result in abortion outbreaks. While the causes of foetal mortality have traditionally been classified as infectious and non-infectious, in fact, the latter category is a diagnosis of exclusion, generally without determination of the non-infectious cause. This review has also established that the traditional dichotomisation of infectious agents into primary and secondary pathogens is based on a flawed premise and these terms should be discontinued. The delicate balance of the maternal gestational immune system between not rejecting the allograft (conceptus) but rejecting (attacking) foetopathogens is stage-of-pregnancy-dependent thus the timing of infection determines the clinical outcome which may result in persistent infection or foetal mortality. Utilisation of our knowledge of the materno-foetal immune responses to foetopathogenic infection has resulted in the development of numerous mono- and polyvalent vaccines for metaphylactic or prophylactic control of bovine foetal mortality. While some of these have been shown to significantly contribute to reducing the risk of both infection and foetal mortality, others have insufficient, or conflicting evidence, on efficacy. However, recent developments in vaccinology, in particular the development of subunit vaccines and those that stimulate local genital tract immunity, show greater promise.

The Efficacy of Vaccination in the Prevention of Renal and Genital Leptospirosis in Experimentally Infected Sheep

(1) Background: Leptospirosis, mainly determined by strains belonging to serogroup Sejroe, has a direct impact on the reproductive efficiency of ruminants, such as sheep. In Brazil, Leptospira santarosai serovar Guaricura, known to be able to chronically colonize the uterine environment, is of special note. Although vaccination minimizes the effects of acute disease, whether or not it can protect from renal colonization remains controversial, and its effects on the genital tract are unknown. In this context, the present study aims to investigate the efficacy of vaccination in the prevention of experimental genital leptospirosis. (2) Methods: Eighteen sheep were divided into three groups: one vaccinated with a polyvalent commercial bacterin, one vaccinated with an autologous bacterin, and one unvaccinated. After 14 days, the sheep were experimentally challenged with 10⁸ leptospires (L. santarosai, serogroup Sejroe, serovar Guaricura, strain FV52) intraperitoneally. Serology and colonization of the urinary and genital tracts were carried out monthly by PCR for 210 days in all animals. (3) Results: Vaccination significantly elicited antibody titers with a predominance of agglutinins against serogroup Sejroe. Both urinary and genital infections were confirmed by PCR. Positivity in urine PCR was absent after D120, while genital infection persisted until the end of the study. Serological results and the finding that vaccination did not avoid renal colonization align with previous studies. Despite vaccination, Leptospira established chronic and asymptomatic colonization of the genital tract until D210, an outstanding finding that remains to be fully understood in its mechanisms. (4) Conclusions: This is the first study conducted to analyze the effects of vaccination in the prevention of genital leptospirosis.

Control of bovine leptospirosis: Aspects for consideration in a tropical environment

Due to the complex and dynamic epidemiology of leptospirosis on livestock, control is still controversial and frustrating. In this context, this paper discusses the main challenges and perspectives for the control of bovine leptospirosis, particularly under tropical conditions. In order to reduce the effects of the disease in cattle, it has been proposed that the control should integrate the trinomial antibiotic therapy (mainly streptomycin); vaccination (whole-cell bacterins); and environmental management. This last element should be carefully considered in tropics. Despite the enormous economic impact of the disease, mainly on its chronic and silent reproductive presentation, research on control programs is not proportional. Conversely, the number of studies regarding the new vaccine strategies, such as recombinant antigens has been increasing and should be encouraged.

A systematic review of leptospirosis on dogs, pigs, and horses in Latin America

Leptospirosis is a worldwide zoonosis which can affect many species. Control programs need accurate diagnosis to be successful, and currently, diagnosis relies on serology. It presents three main issues: the sampling, the antigen panel, and the cutoff point. Herein, we propose a systematic review on leptospirosis among dogs, pigs, and horses in Latin America in order to improve the understanding of the seroepidemiology of leptospirosis in these species in the region as well as the temporal development of the research on this topic and, consequently, improve the chances of success on control programs. Internet databases were consulted over 2015. Inclusion criteria included serosurvey using MAT; a relevant number of animals; the presence in the antigen panel of at least one representative of serogroups Icterohaemorrhagiae and Canicola for dogs, Icterohaemorrhagiae, Australis, and Pomona for pigs, and Icterohaemorrhagiae and Australis for horses; and a cutoff point of ≥100. Overall, 240 papers were studied, of which 87 referred to dogs, 66 to pigs, 39 to horses, and 48 to more than one of the studied species. In relation to those that met all the inclusion criteria, it was 45 (66.2%) in dogs, 23 (41.8%) in pigs, and 23 (63.9%) in horses. Leptospirosis is widespread in Latin America. Predominant serogroups are Canicola to dogs and Icterohaemorrhagiae to pigs and horses. Therefore, research on animal leptospirosis should be encouraged in Latin America, in order to reach a greater standardization in studies and then achieve better results on control programs.

Usage of Leptospira spp. local strains as antigens increases the sensitivity of the serodiagnosis of bovine leptospirosis

Leptospirosis is a zoonotic disease that occurs worldwide, particularly in tropical countries. In livestock the agent is responsible for reproductive problems such as infertility and abortion. Serogroup Sejroe, particularly serovar Hardjo, prevails in cattle in several regions. The microscopic agglutination test (MAT) is the current method for diagnosing leptospirosis. It has been proposed that the inclusion of local strains could detect a larger set of seroreactive animals. In that context, the aim of the present study was to evaluate if the usage of local strains as antigens increases the sensitivity of the serodiagnosis of bovine leptospirosis. Blood and urine samples were collected from 314 bovines from several herds randomly selected in a slaughterhouse in Rio de Janeiro, Brazil. Serological diagnosis was made with MAT using a 21 reference-strains panel (MAT21). Additionally, 12 local strains (MAT33) were included as antigens. PCR was performed with the urine samples and it was positive on 71 out of 222 samples (31.9%). MAT21 identified as seroreactive 173 (55.1%) out of the 314 animals studied, with Sejroe the most common (38.1%). In MAT33, 204 (65.0%) animals were seroreactive with a significant increase on seroreactivity (9.9%). In conclusion, MAT presented with a significant increase of sensitivity when local strains were used as antigens. Among the local strains, 2013_U152 (KP263062) (serogroup Shermani) and 2013_U280 (KP263069) (serogroup Grippotyphosa) showed to be more antigenic.

Avaliação do controle de leptospirose por vacinação em bovinos de propriedade leiteira no estado do Piauí

Neste estudo foram colhidos soros de 255 vacas e 2 touros no período de 2004 a 2009, em intervalos de seis meses, em uma fazenda de gado leiteiro no município de Buriti dos Lopes, Piauí. Pela técnica de soroaglutinação microscópica (SAM), os sorovares de leptospiras encontrados foram Hardjobovis, Hardjoprajitno (Norma), Hardjoprajitno (OMS). Para o controle da leptospirose, foi testada uma vacina contendo os mesmos sorovares encontrados infectando o rebanho. Os resultados mostraram que em bovinos leiteiros na bacia de Parnaíba, no Piauí, ocorre leptospirose, com predominância do sorovar Hardjobovis. A utilização de uma vacina contendo as sorovariedades mais prevalentes no rebanho, aplicada semestralmente ao longo de cinco anos, foi importante para a redução dos títulos de anticorpos, além de reduzir os problemas reprodutivos no rebanho.

Vaccination for leptospirosis improved the weaning percentage of 2-year-old farmed red deer hinds in New Zealand

AIM

To investigate the effect of leptospiral vaccination against serovars Hardjo-bovis and Pomona on fetal loss and weaning percentage in rising 2-year-old farmed red deer hinds.

METHODS

In mid-February 2007, 252 rising 2-year-old hinds on four farms received a single dose of streptomycin (25 mg/kg), to minimise leptospiral infection. They were randomly allocated to vaccinated and control groups. Vaccinated hinds (n=125) received a 2-ml S/C injection of a bivalent whole-cell killed leptospiral vaccine (Leptavoid-2) followed by a booster 4-6 weeks later, and were grazed with control hinds (n=127). These animals were isolated from other hinds on each property, until after mating (June 2007), when all vaccinated and control hinds were combined with hinds not treated with streptomycin, for maximum exposure to natural leptospiral challenge. Evidence of natural challenge by Leptospira spp. was assessed in blood samples from control hinds by serology against L. borgpetersenii serovar Hardjo-bovis and L. interrogans serovar Pomona, using the microscopic agglutination test (MAT), and in hinds not treated with streptomycin by detection of shedding of organisms in urine, using bacterial culture and real-time PCR. Pregnancy diagnosis was carried out in May/June 2007, using transrectal ultrasonography, to determine conception. In late October, prior to calving, the pregnant vaccinated and control hinds were examined by palpation of the abdomen and udder, to determine the percentage of hinds pregnant at term and assess fetal loss. In March 2008, at weaning, vaccinated and control hinds were examined for lactation status, using observation and palpation of the udder. The differences between the groups were evaluated using matched logistic regression analysis.

RESULTS

After mating, pregnancy was diagnosed in 97/125 (77.6%) vaccinated and 106/127 (83.5%) control hinds. All four farms had serological evidence of Hardjo-bovis infection, and a single hind was serologically positive for Pomona between October and March. Real-time PCR confirmed urinary shedding on two farms. The mean percentage of hinds pregnant at term, for those animals confirmed pregnant after mating, in the vaccinated and control groups was 95/97 (98%) (range 95-100%) and 103/106 (97%) (range 94-100%), respectively (p>0.05). The mean weaning percentage for vaccinated and control groups was 86/97 (89%) (range 78-95%) and 88/106 (83%) (range 76-88%), respectively (p=0.015).

CONCLUSION

Vaccination for leptospirosis resulted in no difference in the percentage of hinds pregnant at term, but a higher weaning percentage compared with unvaccinated controls suggesting that vaccination reduced perinatal and/or pre-weaning mortality.

Comparison of Fluorescent Antibody and Microscopic Agglutination Testing for Leptospira in Pregnant and Nonpregnant Cows

Serum and urine samples from 30 cows (15 pregnant and 15 nonpregnant) from each of 10 Georgia dairy herds (total cows = 300) were examined by microscopic agglutination testing (MAT) and direct fluorescent antibody testing (FAT), respectively. Seven of the 10 herds had at least 1 cow with a positive FAT, and all of the herds had at least 1 cow with a reciprocal MAT titer ≥100 for 1 or more serovars. Serological testing was not helpful in identifying the infecting serovar for cows with a positive FAT result. The MAT titers for all 7 of the serovars evaluated were significantly correlated with one another, with 17 (81%) of the 21 Spearman rank correlation coefficients ≥0.4 in magnitude. Twenty (56%) of 36 FAT-positive cows did not have a titer that was highest for any particular serovar. Four of the 7 herds that reported using a Leptospira borgpetersenii serovar Hardjo-bovis vaccine had one or more FAT-positive cows compared with 3 out of 3 herds that reported they were not using this type of vaccine, although this difference was not statistically significant.