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Absence of Host-Specific Hemotropic Mycoplasmas in Horses and Donkeys from Croatia: First Systematic Survey in Southeastern Europe.
Abstract: Hemotropic mycoplasmas (hemoplasmas) are uncultivable, cell wall-less bacteria that parasitizeon the surface of red blood cells of mammals, potentially causing anemia and other systemic signs. While widely distributed among domestic and wild animals, their occurrence in equids remains poorly understood, and no species has been identified as host-specific to horses or donkeys. This study presents the first systematic survey of hemoplasmas in equids from southeastern Europe and only the second molecularly confirmed case in horses in Europe. A total of 843 equids (817 horses and 26 donkeys) from different regions of Croatia, representing various ages, uses, and husbandry systems, were screened for hemoplasmas by PCR targeting the 16S rRNA gene. Only one horse tested positive, identified as , a hemoplasma typically associated with cattle. The estimated prevalence was 0.12% (95% CI: 0.003-0.68%). No donkeys were infected. The extremely low prevalence observed here-the lowest reported in any study detecting hemoplasma-positive horses-supports the hypothesis that equids do not harbor host-specific hemoplasma species and may only sporadically acquire infections from other hosts via spillover. This finding underscores the apparent absence of persistent hemoplasma lineages adapted to equids and highlights the need for further research on their epidemiology, host specificity, and transmission dynamics.
Publication Date: 2026-01-15 PubMed ID: 41594454PubMed Central: PMC12837906DOI: 10.3390/ani16020263Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Overview
- This study investigated the presence of hemotropic mycoplasmas (hemoplasmas), which are bacteria that infect red blood cells, in horses and donkeys from Croatia.
- It found almost no infections, suggesting that horses and donkeys likely do not carry species of these bacteria that are specific to them, but may occasionally get infected from other animals.
Background on Hemoplasmas
- Hemoplasmas are bacteria without cell walls that live on the surface of red blood cells in mammals.
- They can cause anemia and other systemic illnesses in their hosts.
- These bacteria are widespread across many domestic and wild animals but their presence and behavior in equids (horses, donkeys) are not well studied.
- No hemoplasma species has yet been identified as specifically adapted to horses or donkeys.
Objective of the Study
- Conduct the first systematic screening for hemoplasmas in horses and donkeys in Southeastern Europe (specifically Croatia).
- Address gaps in knowledge about whether equids carry host-specific hemoplasma species or only acquire infections sporadically from other hosts.
Methodology
- Total Sample Size: 843 equids, with 817 horses and 26 donkeys.
- Sampling across various Croatian regions encompassing different ages, uses (work, sport, etc.), and husbandry systems.
- Testing Technique: PCR (Polymerase Chain Reaction) targeting the 16S rRNA gene was used to detect hemoplasmas.
- Sequence analysis was used for species identification of any hemoplasmas detected.
Key Findings
- Only one horse tested positive out of 843 animals examined, corresponding to a prevalence rate of 0.12% (with a 95% confidence interval between 0.003% and 0.68%).
- No donkeys tested positive for hemoplasmas.
- The detected hemoplasma species was typically associated with cattle, not a species known to be adapted to equids.
- This prevalence is the lowest reported in European horses and possibly worldwide in studies detecting hemoplasma-positive equids.
Interpretations and Implications
- The extremely low prevalence supports the hypothesis that horses and donkeys do not harbor their own specialized, host-specific hemoplasma species.
- Equids may only acquire hemoplasma infections incidentally through spillover events from other host species such as cattle.
- There is no evidence of persistent hemoplasma lineages adapted to horses or donkeys in Croatia or likely Southeastern Europe.
- Findings highlight the need for further research on:
- The detailed epidemiology of hemoplasmas in equids
- The transmission mechanisms, including vectors or direct contact pathways
- Host specificity and potential risks for horses and donkeys in mixed-species environments
Significance of the Study
- Provides the first large-scale, systematic molecular survey of hemoplasmas in equids in Southeastern Europe, filling an important geographic gap.
- Reinforces the understanding that horses and donkeys are unlikely to be significant reservoirs of hemoplasma infections.
- Offers a baseline prevalence estimate that can be compared with future studies monitoring changes in infection rates or emergence of new host-specific strains.
Cite This Article
APA
Konstantinović N, Gotić J, Baban M, Csik G, Listeš E, Gagović E, Jurković Žilić D, Arežina I, Šubara G, Čulina FE, Delić N, Višal D, Zvonar Z, Beck R, Kostelić A.
(2026).
Absence of Host-Specific Hemotropic Mycoplasmas in Horses and Donkeys from Croatia: First Systematic Survey in Southeastern Europe.
Animals (Basel), 16(2), 263.
https://doi.org/10.3390/ani16020263 Publication
Researcher Affiliations
- Faculty of Veterinary Medicine, University of Zagreb, 10 000 Zagreb, Croatia.
- Faculty of Veterinary Medicine, University of Zagreb, 10 000 Zagreb, Croatia.
- Faculty of Agrobiotechnical Sciences Osijek, J.J. Strossmayer University, 31 000 Osijek, Croatia.
- Veterinary Clinic Equivet d.o.o., 10 000 Zagreb, Croatia.
- Linkomed Veterina d.o.o., 21 230 Sinj, Croatia.
- Croatian Veterinary Institute, 10 000 Zagreb, Croatia.
- Croatian Veterinary Institute, 10 000 Zagreb, Croatia.
- Veterinary Clinic Gospić, 53 000 Gospić, Croatia.
- Agency for Rural Development of Istria (AZRRI), 52 000 Pazin, Croatia.
- Faculty of Veterinary Medicine, University of Zagreb, 10 000 Zagreb, Croatia.
- Faculty of Veterinary Medicine, University of Zagreb, 10 000 Zagreb, Croatia.
- Faculty of Veterinary Medicine, University of Zagreb, 10 000 Zagreb, Croatia.
- Miagro Veterina d.o.o., 31500 Lipine, 10 000 Zagreb, Croatia.
- Croatian Veterinary Institute, 10 000 Zagreb, Croatia.
- Faculty of Agriculture, University of Zagreb, 10 000 Zagreb, Croatia.
Conflict of Interest Statement
Author Goran Csik was employed by the company Veterinary Clinic Equivet d.o.o. Author Ema Listeš was employed by the company Linkomed Veterina d.o.o. Author Zlatko Zvonar was employed by the company Miagro Veterina d.o.o. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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