Leptospirosis is one of the most common zoonotic infections and a major problem in terms of both veterinary medicine and public health. However, the disease is under-recognised and under-diagnosed worldwide, particularly in horses. Clinical leptospirosis in horses is mainly associated with recurrent uveitis (ERU), which has recently been studied more intensively, and reproductive disorders, the epidemiology of which is still relatively poorly understood. To enhance our comprehension of abortions caused by leptospirosis in horses and to identify the causative strains, a serological study was carried out with subsequent molecular characterisation of the isolate obtained. Using the microscopic agglutination test (MAT), serum samples from mares that aborted and foetal fluids (when available) were tested for antibodies against Leptospira spp. Furthermore, bacteria isolation from kidney cultures was conducted. Of 97 mare serum samples, 21 (21.64%) tested positive, with Grippotyphosa and Pomona being the most frequently detected serogroups. A significantly higher seroprevalence was found in aborting mares compared to the healthy horse population from the same geographical area, as well as a pronounced seasonal variation. Leptospiral antibodies were not detected in any of the foetal fluids, but isolation was successful in 1 case out of 39 (2.56%). Genotyping by multilocus sequence typing (MLST) and core genome multilocus sequence typing (cgMLST) identified the obtained isolate as Leptospira kirschneri, serogroup Pomona, serovar Mozdok. Further surveillance and molecular typing of Leptospira strains causing abortion in horses would be invaluable in understanding the prevalence and impact of leptospirosis on equine reproductive health in Europe.

In early neonatal development of puppies, the microbiome plays a key role in the maturation of the immune and digestive systems and, ultimately, in shaping health status throughout life. According to Barker's theory, conditions during pregnancy, including the maternal microbiome and health, can have a long-lasting impact on neonatal development and vitality. Increasing research confirms the importance of early microbial colonization and its association with diseases not only in the neonatal period but also later in life. In dogs, it has been shown that puppies already possess an initial microbiome at birth, the composition of which largely depends on the mode of delivery. Recent studies clearly indicate differences between the microbiomes of puppies born vaginally and those delivered by caesarean section, which may affect their immune response and overall resilience. The "sterile womb" paradigm is increasingly being challenged, with new evidence suggesting a possible influence of the maternal microbiome on the initial colonization of the neonate. From intrauterine life onwards, a dynamic competition in microbiome formation begins, which can also be influenced by veterinarians - through their knowledge, decisions, and approach to the dam and the litter. The composition of the microbiome, as well as numerous external factors, including irresponsible use of antibiotics, greatly shapes the long-term health status of the animal.

Leptospirosis is a re-emerging zoonosis of wide geographic distribution and high prevalence, significant in domestic and wild animals as well as humans. It may have a notable impact on reproductive health in dogs. The clinical spectrum ranges from mild subclinical infections to severe septicemic disease with renal failure and/or pulmonary hemorrhagic syndrome, often with a high mortality rate. Clinical expression depends on the host's susceptibility, immune status, infectious dose, and the virulence of the infecting serovar or strain. Certain serovars, for still unknown reasons, tend to cause more severe disease manifestations. Reproductive disorders-including embryonic resorption, abortion, and stillbirthare rarely described in the literature, although Leptospira spp. is known to cause transplacental infections. Individual cases of abortion associated with serovars Buenos Aires and Bratislava have been reported, but evidence remains limited and primarily anecdotal. Diagnostic approaches include serological testing (MAT), PCR, and histopathology, though interpretation may be hindered by cross-reactivity and post-vaccinal antibodies. Considering increasing indications of the reproductive impact of Leptospira spp., it should be routinely included in the differential diagnosis of abortion in bitches, especially in endemic areas and in late gestation. Prevention relies on vaccination, rodent control, and strict biosecurity measures, with special focus on breeding females.

Oestrogen belongs to a group of steroid hormones that are mainly synthesised and secreted by the ovaries of mammals. It regulates the differentiation of the reproductive organs and the development and maintenance of the reproductive system. In addition, oestrogen exerts a variety of physiological functions in non-reproductive tissues and organs, including the cardiovascular system, the nervous system, the immune system and the musculoskeletal system. As the most important sex hormone in bitches, oestrogen plays a versatile role in maintaining the health of the musculoskeletal system. It acts via oestrogen receptors (ERa and ERb), which are expressed in bones, muscles, ligaments and tendons. It is known to have a protective effect on intervertebral discs by reducing apoptosis of disc cells, lowering oxidative stress and promoting the expression of antioxidant enzymes. Similar results have been found in women, where the decline in oestrogen levels during menopause accelerates intervertebral disc degeneration and protrusion (IVDD) and increases the risk of back pain, cranial cruciate ligament (CCL) tears, osteoporosis and sarcopenia. In dogs, premature oestrogen loss due to castration also predisposes to these conditions, emphasising the importance of an individual approach when deciding to castrate, particularly in breeds predisposed to IVDD or CCL rupture. To summarise, oestrogen plays a complex but primarily protective role in the musculoskeletal system of bitches: It preserves the disc structure, regulates muscle metabolism and stimulates collagen synthesis in the ligaments. Oestrogen deficiency increases the risk of disc protrusions, CCL ruptures and muscle weakness. These findings emphasise the importance of individual castration decisions and further research into possible hormonal interventions, similar to hormone replacement therapy in women.