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Topic:Pathogens
Pathogens are microorganisms, such as bacteria, viruses, fungi, and parasites, that can cause disease in horses. These microorganisms interact with the equine immune system, often leading to a range of health issues that can affect individual horses or entire populations. Pathogens can be transmitted through various routes, including direct contact, vectors, or environmental exposure. Common equine pathogens include Streptococcus equi, Equine Herpesvirus, and Strongylus vulgaris. Understanding the interactions between equine hosts and pathogens is essential for disease prevention, management, and treatment. This page compiles peer-reviewed research studies and scholarly articles that explore the identification, transmission, and impact of pathogens on equine health.
Analysis of Canadian and Irish forage, oats and commercially available equine concentrate feed for pathogenic fungi and mycotoxins. Respiratory infections, recurrent airway obstruction (RAO) and exercise induced pulmonary haemorrhage (EIPH) are major causes of poor performance in horses. Fungi and mycotoxins are now recognised as a major cause of these conditions. The most notable fungi are Aspergillus and Fusarium. Fungal spores can originate from forage, bedding and feed and, in turn, these fungal spores can produce a series of mycotoxins as secondary metabolites.This study set out to ascertain the degree of fungal and mycotoxin contamination in feed and fodder used in Irish racing yards over a one-year period. Weather c...
Caries in the infundibulum of the second upper premolar tooth in the horse. Swedish equine dental practices have empirically found that the prevalence of infundibular caries as a primary disorder in the first permanent premolar teeth (P2) of the horse upper jaw has increased during the last 10 years. A previously unknown bacterial species, Streptococcus devriesei (CCUG 47155T), which is related to Streptococcus mutans, has recently been isolated from these carious lesions. To understand the aetiology of caries in horses, it is essential to elucidate the relationship between S. devriesei and P2 infundibular caries. Methods: The anterior infundibulum of maxillary P2, or...
Observed prevalence of tick-borne pathogens in domestic animals in Sicily, Italy during 2003-2005. The objective of this study was to characterize the observed prevalence of tick-borne pathogens (TBP) in domestic animals in Sicily, Italy during 2003-2005. Serological (competitive ELISA and indirect immunofluorescence antibody, n = 3299) and DNA tests (polymerase chain reaction and reverse line blot, n = 2565) were conducted on horse, donkey, cattle, sheep, goat, pig and dog samples. Pathogens analysed included Anaplasma, Ehrlichia, Rickettsia, Babesia and Theileria species, and Coxiella burnetii. The most prevalent TBP were Anaplasma and Babesia species. The results reported herein suggeste...
Molecular basis of resistance to macrolides and lincosamides among staphylococci and streptococci from various animal sources collected in the resistance monitoring program BfT-GermVet. In this study, erythromycin- and/or clindamycin-resistant isolates among 248 coagulase-positive and coagulase-variable staphylococci and 500 streptococci, collected all over Germany during 2004-2006 in the resistance monitoring program BfT-GermVet, were investigated for their genetic basis of macrolide and/or lincosamide resistance. Staphylococci were sampled from various disease conditions of dogs/cats or pigs, whereas streptococci were from dogs/cats, pigs or horses. Resistant staphylococci were further identified biochemically to species and subspecies level and tested for the resistance ge...
In vivo expression of and cell-mediated immune responses to the plasmid-encoded virulence-associated proteins of Rhodococcus equi in foals. Rhodococcus equi is a facultative intracellular pathogen that causes pneumonia in foals but does not induce disease in adult horses. Virulence of R. equi depends on the presence of a large plasmid, which encodes a family of seven virulence-associated proteins (VapA and VapC to VapH). Eradication of R. equi from the lungs depends on gamma interferon (IFN-gamma) production by T lymphocytes. The objectives of the present study were to determine the relative in vivo expression of the vap genes of R. equi in the lungs of infected foals, to determine the recall response of bronchial lymph node (BLN)...
Cerebellar abscess due to Rhodococcus equi in an immunocompetent patient: case report and literature review. Rhodococcus equi (R. equi) is a facultative, intracellular, nonmotile, non-spore-forming, gram-positive coccobacillus, primarily causes zoonotic infections that affect grazing animals, mainly horses and foals and is a rare opportunistic pathogen found in severely compromised patients, and most commonly in recent years, in human immunodeficiency virus (HIV)-infected persons. Early cases, most in patients receiving immunosuppressant therapy, were more likely to be successfully treated with antimicrobial agents than cases in AIDS patients, it is emerging as an important pathogen in patients with ...
Capsid protein of eastern equine encephalitis virus inhibits host cell gene expression. Eastern equine encephalitis virus (EEEV) causes sporadic but often severe cases of human and equine neurological disease in North America. To determine how EEEV may evade innate immune responses, we screened individual EEEV proteins for the ability to rescue the growth of a Newcastle disease virus expressing green fluorescent protein (NDV-GFP) from the antiviral effects of interferon (IFN). Only expression of the EEEV capsid facilitated NDV-GFP replication. Inhibition of the antiviral effects of IFN by the capsid appears to occur through a general inhibition of cellular gene expression. For ex...
Toxin production by and adhesive properties of Clostridium difficile isolated from humans and horses with antibiotic-associated diarrhea. Clostridium difficile is a common nosocomial pathogen in humans and animals that causes diarrhea and colitis following antibiotic therapy. Isolates of C. difficile obtained from faecal material from 20 human patients and 6 equine subjects with antibiotic-associated diarrhea were investigated regarding production of toxins A and B, their capacity to adhere to the human intestinal Caco-2 cell line and equine intestinal cells, and for the presence of fimbriae. The results showed that most (17/20) of the human clinical isolates produced both toxins A and B. One of the human isolates proved toxin A...
West Nile virus: recent trends in diagnosis and vaccine development. West Nile virus (WNV) is a mosquito-borne flavivirus, native to Africa, Europe, and Western Asia. In many respects, WNV is an outstanding example of a zoonotic pathogen that has leaped geographical barriers and can cause severe disease in human and horse. Before the emergence of WNV in the USA, only few methods of diagnosis were available. Recently, many changes in the fields of WN diagnosis and prevention have happened. This paper will review all these new tools. After a description of the main concerns in WNV and West Nile (WN) disease in humans and animals, this review will present the main...
In vitro analysis of nonthermal plasma as a disinfecting agent. To determine the effect of nonthermal plasma on Staphylococcus aureus, fibroblasts in monolayer culture, and clean and contaminated skin explants. Methods: Normal skin from euthanized horses. Methods: S aureus organisms were plated and treated with nonthermal plasma followed by bacterial culture to assess viability. Fibroblasts in monolayer culture and the epidermal and dermal surfaces of clean and S aureus-contaminated skin explants were treated. The effects of distance and duration on the response to treatment were compared. Results: Compared with controls, treatment with nonthermal plasma r...
Use of an insect cell culture growth medium to isolate bacteria from horses with effusive, fibrinous pericarditis: a preliminary study. Effusive, fibrinous pericarditis is an uncommon disease entity in horses. In 2001, pericarditis occurred in conjunction with an epizootic in central Kentucky that was associated with exposure to eastern tent caterpillars (ETCs). Bacterial isolation from equine pericardial fluid samples was attempted using an insect cell culture growth medium (ICCGM). Using previously cultured, stored frozen samples from four horses with fibrinous pericarditis, inoculation of 10% blood agar plates yielded no growth, whereas simultaneous inoculation of ICCGM resulted in the isolation of Proprionibacterium acnes,...
Breeding-induced endometritis in mares. Endometritis is a common cause of infertility in broodmares. In the past, the condition was believed to be exclusively the result of bacterial contamination of the uterus. Treatment strategies were focused on preventing bacteria from entering the uterus and on treating mares with signs of endometritis with antibiotics. More recent research on uterine defense mechanisms has increased our understanding of the pathophysiology of equine endometritis. Additional causative agents have been identified, and we have learned to separate uterine infections and a physiologic breeding-induced endometritis ...
In vitro effects of fungi isolated from equine hooves on primary human keratinocytes. The effects of two dermatophytes (Microsporum gypseum and Trichophyton mentagrophytes) and four moulds (Scopulariopsis brevicaulis, Alternaria alternata, Geotrichum candidum and Penicillium spp.) on living keratinocyte cultures were examined in vitro using primary human keratinocytes. Rates of apoptosis of infected cells were determined using a colorimetric TUNEL system which detects the characteristic nuclear DNA fragmentation of apoptotic cells. The cytotoxicity of the individual fungi was tested by quantitatively measuring cytosolic enzyme lactate dehydrogenase, released upon cell lysis, in...
The influence of distance on movement of tabanids (Diptera: Tabanidae) between horses. Two studies evaluated the potential use of spatial barriers to reduce the mechanical transmission of disease agents by tabanids in the Pantanal region of Brazil. Tabanids at stations separated by four different distances (5, 10, 25, and 50m) were marked. In the first study, tabanids were marked and allowed to feed until engorgement or natural interruption occurred and captured if they transferred to the other horse. A total of 2847 tabanids belonging to nine different species were marked. The percentage of tabanids that moved between horses was 10.5 at 5m, 6.8 at 10m, and 4.6 at 25m. In the se...
Pulmonary disposition of tilmicosin in foals and in vitro activity against Rhodococcus equi and other common equine bacterial pathogens. The objectives of this study were to determine the serum and pulmonary disposition of tilmicosin in foals and to investigate the in vitro activity of the drug against Rhodococcus equi and other common bacterial pathogens of horses. A single dose of a new fatty acid salt formulation of tilmicosin (10 mg/kg of body weight) was administered to seven healthy 5- to 8-week-old foals by the intramuscular route. Concentrations of tilmicosin were measured in serum, lung tissue, pulmonary epithelial lining fluid (PELF), bronchoalveolar lavage (BAL) cells, and blood neutrophils. Mean peak tilmicosin conc...
Methicillin-resistant staphylococcal colonization in clinically normal dogs and horses in the community. To evaluate the prevalence of methicillin-resistant staphylococcal (MRS) colonization in clinically normal dogs and horses in the community. Results: Three hundred clinically normal horses and 200 clinically normal dogs were enrolled. One nasal swab was collected from each horse. Two swabs were taken from each dog: (i) from an anterior nare, and (ii) a combination of the perineal area and 0.5 cm into the anus. Enrichment cultures were performed. Methicillin-resistant Staphylococcus aureus (MRSA) was not identified. Methicillin-resistant Staphylococcus intermedius (MRSI) was isolated from the n...
Molecular typing and anti-microbial susceptibility of clinical isolates of Streptococcus equi ssp. zooepidemicus from equine bacterial endometritis. The anti-microbial susceptibility and genetic diversity of 65 strains of Streptococcus equi ssp. zooepidemicus (Sez) isolated from mares presenting clinical signs of endometritis was determined by disk agar diffusion and pulsed field gel electrophoresis (PFGE) methods, respectively. Overall, Sez isolates were susceptible to beta-lactams, enrofloxacin, trimethoprim-sulfamethoxazole and gentamicin. These anti-microbials could be recommended as empiric anti-microbial therapy in cases of endometritis caused by Sez. Pulsed field gel electrophoresis typing revealed a great genetic diversity (56 diff...
Molecular analysis of Clostridium difficile isolates recovered from horses with diarrhea. Clostridium difficile is an important cause of diarrhea in horses, causing sporadic and epidemic disease of varying severity. This study evaluated the molecular characteristics of 48 C. difficile isolates recovered from diarrheic horses admitted to a veterinary hospital by using PCR-ribotyping and toxin gene profile. Additionally, feces were tested for the presence of C. difficile toxin A/B via enzyme immunosorbant assay (EIA) in 38 horses. The toxin genes tcdA, tcdB and cdtB were present in 27 (56.25%), 35 (72.91%) and 2 (4.1%) strains, respectively. Eight isolates (16.6%) were A(-)B(+) varia...
Genetic relatedness and pathogenicity of equine herpesvirus 1 isolated from onager, zebra and gazelle. Equine herpesvirus 1 was isolated from an onager in 1985, a zebra in 1986 and a Thomson's gazelle in 1996 in USA. The genetic relatedness and pathogenicity of these three viruses were investigated based on the nucleotide sequences of the glycoprotein G (gG) gene, experimental infection in hamsters, and comparison with horse isolates. The gG gene sequences of EHV-1 from onager and zebra were identical. The gG gene sequences of the gazelle isolate showed 99.5% identity to those of onager and zebra isolates. The gG gene sequences of EHV-1 isolated from horses were 99.9-100% identical and 98, 98 a...
Enrofloxacin use in a long-distance transport model of equine respiratory disease. Successful clinical management of bacterial pneumonia in horses depends on the administration of an appropriate antimicrobial agent at an adequate dosage and frequency, given by the correct route of administration for an adequate duration. Empiric antimicrobial therapy should be based on the clinician's experience and current veterinary literature. Based on the frequency of Gram-positive bacterial pathogens isolated from horses with bacterial pneumonia, every effort should be made to provide antimicrobial coverage for this class of pathogens. Gram-negative pathogens may co-exist; therefore, br...
In vitro fungistatic and fungicidal activities of silver sulfadiazine and natamycin on pathogenic fungi isolated from horses with keratomycosis. To evaluate the in vitro antifungal properties of silver sulfadiazine (SSD) and natamycin against filamentous fungi isolated from eyes of horses with keratomycosis. Methods: Filamentous fungal isolates obtained from eyes of keratomycosis-affected horses. Methods: Fungal culture of ocular samples yielded 6 Fusarium spp; 7 Aspergillus spp; and 1 isolate each of Curvularia, Scopulariopsis, Penicillium, and Chrysosporium. For each fungal isolate, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of SSD and natamycin were determined. Results: For all 17 fungal isolat...
Identification and characterization of the heme-binding proteins SeShp and SeHtsA of Streptococcus equi subspecies equi. Heme is a preferred iron source of bacterial pathogens. Streptococcus equi subspecies equi is a bacterial pathogen that causes strangles in horses. Whether S. equi has a heme acquisition transporter is unknown. Results: An S. equi genome database was blasted with the heme binding proteins Shp and HtsA of Streptococcus pyogenes, and found that S. equi has the homologue of Shp (designated SeShp) and HtsA (designated SeHtsA). Tag-free recombinant SeShp and SeHtsA and 6xHis-tagged SeHtsA (SeHtsAHis) were prepared and characterized. Purified holoSeShp and holoSeHtsA bind Fe(II)-protoporphyrin IX (h...
Presence of new mecA and mph(C) variants conferring antibiotic resistance in Staphylococcus spp. isolated from the skin of horses before and after clinic admission. Because of the frequency of multiple antibiotic resistance, Staphylococcus species often represent a challenge in incisional infections of horses undergoing colic surgery. To investigate the evolution of antibiotic resistance patterns before and after preventative peri- and postoperative penicillin treatment, staphylococci were isolated from skin and wound samples at different times during hospitalization. Most staphylococci were normal skin commensals and belonged to the common coagulase-negative group. In some cases they turned out to be opportunistic pathogens present in wound infections. M...
Cytokine gene signatures in neural tissue of horses with equine protozoal myeloencephalitis or equine herpes type 1 myeloencephalopathy. This study was designed to determine the relative levels of gene transcription of selected pathogens and cytokines in the brain and spinal cord of 12 horses with equine protozoal myeloencephalitis (EPM), 11 with equine herpesvirus type 1 (EHV-1) myeloencephalopathy, and 12 healthy control horses by applying a real time pcr to the formalin-fixed and paraffin-embedded tissues. Total rna was extracted from each tissue, transcribed to complementary dna (cDNA) and assayed for Sarcocystis neurona, Neospora hughesi, EHV-1, equine GAPDH (housekeeping gene), tumour necrosis factor (TNF)-alpha, interfer...
Gentamicin concentrations in synovial fluid obtained from the tarsocrural joints of horses after implantation of gentamicin-impregnated collagen sponges. To determine synovial fluid gentamicin concentrations and evaluate adverse effects on the synovial membrane and articular cartilage of tarsocrural joints after implantation of a gentamicin-impregnated collagen sponge. Methods: 6 healthy adult mares. Methods: A purified bovine type I collagen sponge impregnated with 130 mg of gentamicin was implanted in the plantarolateral pouch of 1 tarsocrural joint of each horse, with the contralateral joint used as a sham-operated control joint. Gentamicin concentrations in synovial fluid and serum were determined for 120 hours after implantation by use of ...
Genome of horsepox virus. Here we present the genomic sequence of horsepox virus (HSPV) isolate MNR-76, an orthopoxvirus (OPV) isolated in 1976 from diseased Mongolian horses. The 212-kbp genome contained 7.5-kbp inverted terminal repeats and lacked extensive terminal tandem repetition. HSPV contained 236 open reading frames (ORFs) with similarity to those in other OPVs, with those in the central 100-kbp region most conserved relative to other OPVs. Phylogenetic analysis of the conserved region indicated that HSPV is closely related to sequenced isolates of vaccinia virus (VACV) and rabbitpox virus, clearly grouping to...
Rhodococcus equi in the soil environment of horses in Inner Mongolia, China. Little is known about the distribution of Rhodococcus equi in the soil environment of native horses in China. One hundred and eight soil samples were collected from native-horse farms in the Hulun Beier grasslands of eastern Mongolia, the Xilin Goler grasslands of southern Mongolia, and Tongliao City in Inner Mongolia, China. The isolation rates of R. equi from soil samples from the Hulun Beier and Xilin Goler grasslands ranged from 25.9% to 30.0%. In contrast, isolation rates from soil samples from Tongliao City were as high as 82.3% and the mean number of R. equi in soil samples from Tonglia...
Pathophysiology, diagnosis, and management of urinary tract infection in horses. Equine urinary tract infection (UTI) most commonly occurs as a sequela to structural or functional inhibition of normal urine flow. Although it is an infrequent diagnosis in equids, the incidence of UTI in human beings is high and has inspired great investigative effort. The resultant findings with potentially broad application as well as current equine studies are reviewed here. Recent developments in the understanding of host-agent interactions and renal defense mechanisms, emerging antimicrobial resistance, and novel therapeutic alternatives to prophylactic antibiotic use are emphasized.
Osteomyelitis in horses. Much has been learned in the past decade about osteomyelitis. The inhibitory mechanisms of the "biofilm slime" layer that is formed by bacterial extracapsular exopolysaccharides and binds to bone, joints, and implants are now better understood than in the past. The surface colonization of bacteria that occurs within these biofilms is a biologic phenomenon that is somewhat unique to orthopedic infections. This survival strategy of bacteria is effective, and it is important for veterinarians who treat osteomyelitis to be aware of current diagnostic and therapeutic treatment modalities. The pract...
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 managem...
