The prevalence of antibodies to serovars of Leptospira interrogans in horses

A Scoping Review of the Global Distribution of Causes and Syndromes Associated with Mid- to Late-Term Pregnancy Loss in Horses between 1960 and 2020

Equine pregnancy loss is frustrating and costly for horse breeders. The reproductive efficiency of mares has significant implications for a breeding operation’s economic success, and widespread losses can have a trickle-down effect on those communities that rely on equine breeding operations. Understanding the causes and risks of equine pregnancy loss is essential for developing prevention and management strategies to reduce the occurrence and impact on the horse breeding industry. This PRISMA-guided scoping review identified 514 records on equine pregnancy loss and described the global spatiotemporal distribution of reported causes and syndromes. The multiple correspondence analysis identified seven clusters that grouped causes, syndromes, locations and pathology. Reasons for clustering should be the focus of future research as they might indicate undescribed risk factors associated with equine pregnancy loss. People engaged in the equine breeding industry work closely with horses and encounter equine bodily fluids, placental membranes, aborted foetuses, and stillborn foals. This close contact increases the risk of zoonotic disease transmission. Based on this review, research is required on equine abortion caused by zoonotic bacteria, including Chlamydia psittaci, Coxiella burnetii and Leptospira spp., because of the severe illness that can occur in people who become infected.

Detection of Coxiella burnetii and equine herpesvirus 1, but not Leptospira spp. or Toxoplasma gondii, in cases of equine abortion in Australia - a 25 year retrospective study

Equine abortion is a cause of severe economic loss to the equine industry. Equine herpesvirus 1 is considered a primary cause of infectious abortion in horses, however other infectious agents can also cause abortion. Abortions due to zoonotic pathogens have implications for both human and animal health. We determined the prevalence of Coxiella burnetii, Leptospira spp. and Toxoplasma gondii in 600 aborted equine foetal tissues that were submitted to our diagnostic laboratories at the University of Melbourne from 1994 to 2019. Using qPCR we found that the prevalence of C. burnetii was 4%. The highest annual incidence of C. burnetii was observed between 1997-2003 and 2016-2018. The prevalence of C. burnetii in Victoria and New South Wales was 3% and 6% respectively. All the samples tested negative for Leptospira spp. and Toxoplasma gondii DNA. Equine herpesvirus 1 DNA was detected at a prevalence of 3%. This study has provided evidence for the presence of C. burnetii in equine aborted foetal tissues in Australia, but the role of C. burnetii as potential cause of abortion in Australia requires further investigation. C. burnetii is a zoonotic disease agent that causes the disease 'Q fever' in humans. We recommend that appropriate protective measures should be considered when handling material associated with equine abortions to reduce the risk of becoming infected with C. burnetii.

Leptospiral antibody prevalence and surgical treatment outcome in horses with Equine Recurrent Uveitis (ERU) in Switzerland

OBJECTIVE

To evaluate leptospiral antibody prevalence in 65 horses with ERU and compare outcome in 36 surgically treated eyes (2010-2015).

PROCEDURES

Retrospective data analysis of horses with ERU (n = 65). C-value calculation with microagglutination assay titer (MAT) results for Leptospira spp. Evaluation of follow-up data after pars plana vitrectomy (PPV, n = 21 eyes) and suprachoroidal cyclosporine device implantation (SCDI, n = 15 eyes). Differences between groups were statistically analyzed using Fishers exact test, significance set at P < .05.

RESULTS

Positive leptospiral titers were found in 28/65 blood, 31/65 aqueous humor (AH), and 19/20 vitreal (post-PPV) samples. The most common intraocular serovars were Leptospira interrogans grippotyphosa, pomona, and bratislava. Intraocular antibody production was suspected in samples of 22 horses (c-values > 1). Mean follow-up of surgical cases was 3.8 years (PPV) and 3.4 years (SCDI). PPV was performed in 21 eyes with positive, SCDI in 15 eyes with negative leptospiral test results. Uveitis recurred less often after PPV (2/21) compared to SCDI (6/15, P = .04). Retinal detachment occurred after PPV only (5/21, SCDI 0/15, P = .06), whereas only SCDI-treated eyes were enucleated (PPV 0/21, SCDI 3/15, P = .06). Blindness or visual impairment was equally likely to occur in both treatment groups after surgery (PPV 7/21, SCDI 7/15, P = .5).

CONCLUSIONS

Leptospiral antibody prevalence is high in horses with ERU in Switzerland. Recurrence of uveitis is uncommon following PPV in the present study; an increased risk of retinal detachment exists. Enucleation is more often warranted in horses after SCDI in this study due to a higher uveitis recurrence.

The epidemiology of leptospirosis and the emergence of Leptospira borgpetersenii serovar Arborea in Queensland, Australia, 1998-2004

Leptospirosis is one of the most commonly encountered zoonoses in both Australia and the rest of the world. The incidence of leptospirosis in Queensland over the 7-year study period (1998-2004) was 3.1/100000 population. Enhanced surveillance questionnaires were used to collect patient data and facilitate an epidemiological investigation of leptospirosis in Queensland. Farming occupations comprised the majority of occupational exposure cases, however, recreational exposure accounted for 18% of the 883 cases. Rainfall and the presence of animal hosts had the most influence on the incidence of leptospirosis. Several trends in serovar numbers over this period are noted, in particular the emergence of L. borgpetersenii serovar Arborea, which accounted for 22% of all leptospirosis cases in Australia and 68% of South-East Queensland cases in 2004. Assessment of epidemiological trends in leptospirosis is important to obtain directed public health intervention and outcomes in the reduction of leptospirosis cases.

Infections of the Head and Ocular Structures in the Horse

Infectious conditions of the equine head are commonly encountered in clinical practice. Pathogenic bacterial, viral, and fungal organisms may localize in the extensive nasal passages, paranasal sinuses, and guttural pouches, creating a range of clinical signs and conditions that can be severe enough to lead to unexpected fatality. Renewed interest in equine dentistry has led to a greater recognition of dental disease that is associated with infection. This article focuses on bacterial and fungal infections of the main anatomic regions of the equine head, where advances in diagnosis and management have been made or consolidated in recent years. It also addresses recent advances made in the area of infectious equine corneal disease, including bacterial, viral, and fungal etiologies. Recent developments in equine recurrent uveitis as it relates to infectious diseases and ocular manifestations of systemic disease are also discussed.

Emergent causes of placentitis and abortion

The clinical signs, laboratory findings, diagnosis, epidemiology, treatment, and prevention and control of two emerging causes of placentitis and abortion in horses are described in this article. Leptospirosis has been reported as a significant cause of fetal loss in horses in Kentucky, Northern Ireland, and England. Most abortions result from infection by serovars kennewicki or bratislava. Nocardioform placentitis has become the most common cause of placentitis in central Kentucky horses. Nocardioform placentitis is associated with infection by unnamed, gram-positive, filamentous, branching bacteria, and is characterized by distinctive changes in the placental membranes.

Detection of Leptospira spp. in the aqueous humor of horses with naturally acquired recurrent uveitis

Leptospiral organisms have long been presumed to be associated with the presence of equine recurrent uveitis. This project was undertaken to determine the presence of Leptospira spp. in the aqueous humor of horses with uveitis to determine if there was an association with inflammation. Thirty horses were determined to have recurrent uveitis based on clinical evaluation or history. Sixteen horses were judged clinically and historically to be free of uveitis and were used as controls. Aqueous humor samples were cultured and evaluated by PCR for the presence of Leptospira DNA. Serum was collected and evaluated for the presence of antibodies against five serovars in a leptospirosis panel. Twenty-one of 30 horses with recurrent uveitis and one of 16 uveitis-free horses were positive by PCR for the presence of Leptospira DNA. Six of these 21 horses with uveitis were culture positive for leptospires from the aqueous humor. Serologic results did not correlate well with the presence of Leptospira DNA or organisms in the aqueous humor. Leptospira spp. are present in a high percentage of horses with naturally occurring recurrent uveitis.

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.

An outbreak of abortion in mares associated with Salmonella abortusequi infection

An abortion outbreak occurred in a herd of 38 horses, 26 of which were pregnant mares. Twenty-one mares aborted between 5-10 months of gestation. In no case were there indications of impending abortion. Pathoanatomical, histopathological, virological and bacteriological examinations were carried out on 4 aborted fetuses. Histopathology identified Gram-negative bacteria compatible with salmonella in all 4 placentae. By subsequent bacteriological examination Salmonella abortusequi was isolated as the single causative agent in each case. Nonmotile Salmonella abortusequi with antigenic formula 4,12:-:- was isolated from one of the 4 fetuses. The described episode of equine abortion clearly indicates that Salmonella abortusequi has not been eradicated from Europe as previously thought.

Serological and microbiological findings on 3 farms with equine leptospiral abortions

Blood and urine samples from horses on 3 central Kentucky horse farms with prior histories of leptospiral abortions were analysed. Blood samples were obtained from all available horses on each farm and tested for antibodies to 6 leptospira serovars. Urine samples were collected from non-gravid mares with serum antibody titres > or = 1:800 and examined for leptospires by dark-field microscopy, fluorescent antibody testing and culture. Adult horses had the greatest serological evidence of exposure to leptospira, followed by yearlings, then foals. Of horses with anti-leptospiral antibodies, 76.3% reacted against serovar bratislava, 49.1% against icterohaemorrhagiae, 20.1% against grippotyphosa, 16.3% against pomona genotype kennewicki, 15.9% against hardjo and 1.0% against canicola. These findings confirmed that horses in central Kentucky are exposed to multiple leptospira serovars. The seroprevalence of antibodies to the 6 selected serovars was consistent among the 3 selected farms. There was no direct correlation between the serovar that was the cause of abortion in the previous season and prevalence of positive titres to that serovar in horses tested on the farms in the following year. Furthermore, there was no evidence of long-term urinary shedding of leptospira by horses with high leptospira antibody titres.

Leptospirosis

Equine clinical leptospirosis has been primarily related to uveitis and the often recurrent sequelae of ocular changes. Reports of equine hepatic and renal involvement are sporadic. More recently, serovar bratislava has been identified as a host-adapted serovar in the horse. More significantly, reports of equine abortion and stillbirth have become more frequent in the literature. This is more than likely a result of improved diagnostic techniques, not of increased prevalence of disease. In addition to abortion, equine neonatal disease is becoming more frequently recognized in association with leptospira infection. Whether leptospiral infection results in abortion or diseased foals may depend upon the stage of gestation when the mare is exposed and host immune status. Antibiotic of choice for treatment of equine leptospirosis remains speculative, as specific equine studies have not been performed. Extrapolation from other species suggests that the use of streptomycin remains a good choice of therapy for the chronic shedding state and may be used in combination with other antimicrobials for treatment of acute disease. Penicillin or potentiated penicillins and tetracycline at appropriate to high end dosages are logical choices for the treatment of acute leptospirosis.

Leptospirosis in equine fetuses, stillborn foals, and placentas

Leptospirosis was diagnosed in 51 equine fetuses and 16 stillborn foals with gestational ages from 3 1/2 to 11 months. Diagnosis was based on one or more of the following: positive fetal antibody titer, positive fluorescent antibody test, demonstration of spirochetes in kidney and/or placental sections stained by the Warthin-Starry technique, high leptospiral titers in aborting mares, or isolation of Leptospira spp. from fetal organs. Gross lesions were observed in 80.3% of the fetuses, stillborn foals, and placentas. Gross placental lesions included nodular cystic allantoic masses, edema, areas of necrosis of the chorion, and necrotic mucoid exudate coating the chorion. The liver (23 cases) was enlarged, mottled, and pale to yellow. The kidneys (seven cases) were swollen and edematous with pale white radiating streaks in cortex and medulla. Microscopic lesions were observed in 96% of fetuses, stillborn foals, and placentas. Placental lesions consisted of thrombosis, vasculitis, mixed inflammatory cell infiltration of the stroma and villi, cystic adenomatous hyperplasia of allantoic epithelium, and villous necrosis and calcification. Fetal lesions included hepatocellular dissociation, mixed leukocytic infiltration of the portal triads, giant cell hepatopathy, suppurative and nonsuppurative nephritis, pulmonary hemorrhages, pneumonia, and myocarditis. Spirochetes were demonstrated with the Warthin-Starry stain in the allantochorion and/or kidney of 69 of the 71 cases. Using the direct fluorescent antibody technique, 56/60 cases tested positively for leptospires. Leptospires were isolated from fetal tissues in 20/42 cases. Sixteen of the isolates were identified by restriction enzyme analysis as Leptospira interrogans serogroup Pomona serovar kennewicki; case Nos. 36 and 41 were serovar grippotyphosa.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis and prevalence of leptospira infection in aborted and stillborn horses

A study was conducted to evaluate a recently available fluorescent antibody test (FAT) conjugate for the detection of leptospires in tissues of aborted and stillborn horses, to determine the leptospira antibody titers and compare serologic test results with FAT results, and to determine the prevalence of leptospira-induced abortions and stillbirths in the equine population of central Kentucky. From July 1, 1988 through June 30, 1989, 15 (2.5%) of 594 submissions (fetuses, stillborn foals, and/or placentas) were diagnosed as leptospirosis by the FAT (14 of 15 tested) and/or microscopic agglutination test (12 of 14 tested). Of the 12 serologically positive fetal fluids, 10 had high tigers against Leptospira interrogans serovar pomona and 2 against serovar grippotyphosa.