Pneumonia in horses is a respiratory condition characterized by inflammation of the lungs, often caused by bacterial, viral, or fungal infections. It can affect horses of all ages, though young and immunocompromised animals are more susceptible. Clinical signs of pneumonia in horses may include coughing, nasal discharge, fever, and labored breathing. Diagnosis typically involves a combination of clinical examination, imaging techniques such as radiography or ultrasonography, and laboratory tests including blood work and microbial cultures. Treatment strategies vary depending on the underlying cause and may involve antimicrobial therapy, supportive care, and environmental management. This page compiles peer-reviewed research studies and scholarly articles that explore the etiology, pathophysiology, diagnosis, and treatment of pneumonia in equine populations.
Melo UP, Ferreira C, Barreto SWM.Respiratory diseases considerably affect equine athletes, being the second most common cause of poor performance. Among these diseases, fungal pneumonia in horses, caused specifically by Aspergillus spp., is relatively rare but potentially fatal. Fungal pneumonia typically affects horses exposed to fungal elements due to environmental factors, immunosuppression, or previous debilitating illnesses. Treatment is complex, with minimal success due to late diagnosis and serious concomitant underlying diseases. The choice of medication depends on the site of infection, the fungal species involved, a...
Berghaus LJ, Cathcart J, Berghaus RD, Ryan C, Toribio RE, Hart KA.Rhodococcus equi (R. equi), a pneumonia-causing intracellular bacterium, results in significant morbidity and mortality in young foals, while healthy adult horses rarely develop disease. Survival and replication within alveolar macrophages (AMφ) are the hallmarks of R. equi's pathogenicity. The vitamin D receptor (VDR) and its ligand, the active vitamin D metabolite 1,25(OH)2D, are important in immune responses to intracellular bacteria. The vitamin D/VDR pathway regulates the downstream production of cytokines in infected human AMφ. The immunomodulatory role of the vitamin D/VDR pathway in ...
Laclaire AL, Manguin E, Tanquerel L.Effects of general anesthesia with controlled ventilation on the respiratory system have had limited evaluation in horses. A prospective observational study was performed with eleven client-owned horses undergoing elective surgery. Physical examination, auscultation with a rebreathing bag, complete blood cell count, lung ultrasound imaging, tracheal endoscopy imaging and transendoscopic tracheal wash were conducted before and 24 hours after anesthesia. Lung ultrasound imaging was also repeated just after recovery. A significant increase in blood neutrophil count between pre- and post-anesthesi...
İncili CA, Eröksüz Y, Otlu B, Kara E, Tanrıverdi ES, Timurkan MÖ, Kalender H, Eröksüz H.Moellerella wisconsensis is a Gram-negative, facultative anaerobic bacillus of Entero-bacteriaceae family, and it is an uncommon pathogen in domestic animals. To date, five cases were reported including two dogs, two cattle, and a goat. Streptococcus equisimilis is the second common bacterial agent after the S. equi subsp. zooepidemicus in equine pneumonia cases. The present report describes the isolation of M. wisconses from lungs and spleen of a 10-year-old Arabian horse (May 08, 2022) at post-mortem examination being co-infected with S. equisimilis. Clinical and pathological findings includ...
Rakowska A, Czopowicz M, Bereznowski A, Witkowski L.Rhodococcus equi is a widely recognized bacterium responsible for pneumonia in preweaned foals. On endemic farms, foals with a subclinical course of the disease usually outnumber those presenting clinical signs. The disease is typically chronic and mainly manifests as fever and dyspnoea. Currently, field diagnosis is often based on lung ultrasound (LUS); however, both diagnostic and therapeutic approaches vary among practitioners and considerably change over time. This longitudinal, prospective study was designed to describe the appearance and progression of rhodococcal pulmonary lesions durin...
Tsuzuki N, Maruko T, Takeyama A, Ikeda H, Mizuguchi Y.Forty-five foals with Rhodococcus equi infection and pneumonia symptoms were classified into a surviving group and a dead group. Using serum samples, the oxidative stress index (OSI) was determined at the first visit and the follow-up visit. The OSI of the surviving group was significantly lower at the follow-up than that at the first visit. No significant difference was observed between the OSI of the dead group at the first and follow-up visits. In the surviving group, treatment at the first visit mitigated inflammation and reduced OSI. However, in the dead group, poor response to the treatm...
Bohlman T, Waddell H, Schumaker B.The occurrence of zoonotic infections following an animal exposure continues to be an important consideration for all patients, especially those within agricultural communities. Streptococcus equi subspecies equi (S. equi subsp. equi) is a bacteria known to cause a common infection called 'Strangles' in horses. This article highlights a new case of pneumonia and bacteremia in a patient caused by S. equi subsp. equi following strangles exposure in a horse. Rarely has there been reported horse to human transmission of subsp. equi. Methods: A 70-year-old woman attended a rural emergency departmen...
Hepworth-Warren KL, Estell K, Cowles B, Amodie D, Crisman M.Serum amyloid A (SAA) is a major acute phase protein in horses which could be a useful tool for assessing clinical response to treatment of bacterial pneumonia in adult horses.
Bergmann R, Schroedl W, Müller U, Baums CG.Streptococcus equi subsp. zooepidemicus (SEZ) is a major equine pathogen that causes pneumonia, abortion, and polyarthritis. It can also cause invasive infections in humans. SEZ expresses the M-like protein SzM, which recruits host proteins such as fibrinogen to the bacterial surface. Equine SEZ strain C2, which binds only comparably low amounts of human fibrinogen in comparison to human SEZ strain C33, was previously shown to proliferate in equine and human blood. As the expression of SzM_C2 was necessary for survival in blood, this study investigated the working hypothesis that SzM_C2 inhibi...
Zúñiga MP, Badillo E, Abalos P, Valencia ED, Marín P, Escudero E, Galecio JS.Rhodococcus equi is responsible for foal pneumonia worldwide, with a significant economic impact on the production and breeding of horses. In Chile, the first case was reported in 2000, and since then, its incidence has been increasing. Distinctive characteristics of R. equi as an intracellular pathogen in macrophages, emergence of virulence plasmids encoding surface lipoprotein antigens, and appearance of antibiotic resistance against macrolides and rifampicin have significantly complicated the treatment of R. equi pneumonia in foals. Therefore, in vitro susceptibility studies of first-line a...
Higgins C, Huber L.Rhodococcus equi, a gram-positive facultative intracellular pathogen and a soil saprophyte, is one of the most common causes of pneumonia in young foals. It poses a threat to the economy in endemic horse-breeding farms and to animal welfare annually. Many farms use thoracic ultrasonographic screening and antimicrobial treatment of subclinically affected foals as a preventive measure against severe R. equi infections. The wide use antimicrobials to treat subclinically affected foals has contributed to the emergence of multidrug resistant (MDR)-R. equi in both clinical isolates from sick foals a...
van der Vossen N, Cavalcante P, Glynn S, Achappa D, Mehmood W, Oikawa M, Vinardell T, Jamieson C.Upper respiratory disease was reported over many seasons in Arabian foals on a single stud farm in the Middle East. Affected foals were noted to have mucopurulent nasal discharge, cough, fever and tachypnea. All affected foals had been empirically treated with a macrolide and rifampicin, by the referring veterinarian without improvement. On endoscopic examination, all affected foals had significant guttural pouch empyema (GPE). (1) To document a previously unreported presentation of guttural pouch empyema (GPE) in a family of juvenile Arabian foals; (2) To document the cytological and microbia...
van Spijk JN, Beckmann K, Wehrli Eser M, Stirn M, Steuer AE, Saleh L, Schoster A.Neuro- and nephrotoxicity of polymyxins are known but clinical studies in horses are lacking. The aim of this study was to describe neurogenic and nephrogenic side effects of hospitalized horses receiving Polymyxin B (PolyB) as part of their treatment plan. Twenty horses diagnosed with surgical colic ( = 11), peritonitis ( = 5), typhlocolitis ( = 2), pneumonia, and pyometra (each = 1) were included. Antimicrobial treatment was randomized to GENTA (gentamicin 10 mg/kg bwt q24 h IV, penicillin 30.000 IU/kg q6 h IV) or NO GENTA (marbofloxacin 2 mg/kg bwt q24 h IV, penicillin 30.000 IU/kg q6 h IV...
Berghaus LJ, Cathcart J, Berghaus RD, Hart KA.The vitamin D receptor (VDR)-vitamin D axis modulates pulmonary immunity in people but its role in equine immunity is unknown. Bacterial pneumonia causes high morbidity/mortality in foals and alveolar macrophages (AMφ) are important for pulmonary defenses. Age-related variations in vitamin D-mediated function of AMφ might contribute to the foal's susceptibility to pneumonia. Our aim was to assess the impact of age on equine vitamin D metabolism and VDR expression in AMφ. AMφ and plasma was collected from healthy foals (2, 4 and 8 weeks old) and adult horses (once). AMφ VDR expression was ...
Jones LM, Hawes PC, Salguero FJ, Castillo-Olivares J.African Horse Sickness (AHS) is a vector-borne viral disease of equids. The disease can be highly lethal with mortality rates of up to 90% in non-immune equine populations. The clinical presentation in the equine host varies, but the pathogenesis underlying this variation remains incompletely understood. Various small animal models of AHS have been developed over the years to overcome the financial, bio-safety and logistical constraints of studying the pathology of this disease in the target species. One of the most successful small animal models is based on the use of interferon-alpha gene kn...
Sanz MG.Foals become infected shortly after birth; most develop subclinical pneumonia and 20% to 30% develop clinical pneumonia that requires treatment. It is now well established that the combination of screening programs based on thoracic ultrasonography and treatment of subclinical foals with antimicrobials has led to the development of resistant Rhodococcus equi strains. Thus, targeted treatment programs are needed. Administration of R equi-specific hyperimmune plasma shortly after birth is beneficial as foals develop less severe pneumonia but does not seem to prevent infection. This article provi...
Ghallab RS, El-Beskawy M, El-Shereif AA, Rashad AMA, Elbehiry MA.Equine endometritis is one of the most common causes of reproduction failure. To achieve better treatment outcomes, different diagnostic methods should be combined. In the current study, 39 repeat breeder mares were subjected to ultrasonography examination to detect excessive accumulation of intrauterine fluids and an abnormal oedema pattern, which revealed that 61.5% of mares were positive. Combined with endometrial cytology by low-volume uterine flush, 47.7% of smears contain neutrophils (more than 2-3 per HPF X100), and microbial culture. 92.3% of mares were infected with different bacteria...
Hepworth-Warren KL, Nelson NC, Dembek KA, Young KAS.To compare thoracic ultrasonographic findings in healthy horses before and after general anesthesia for elective MRI utilizing a recently developed ultrasonographic scoring system to aid clinicians in the early identification of pneumonia following anesthesia. 13 adult horses > 3 years of age. Prior to anesthesia, horses underwent a thorough physical examination, CBC, thoracic radiography, and thoracic ultrasonography. Horses were then anesthetized for elective MRI, and thoracic ultrasonography was repeated within 3 hours after recovery. Thoracic ultrasonographic findings were scored utilizing...
Kamali M, Carossino M, Del Piero F, Peak L, Mitchell MS, Willette J, Baker R, Li F, Kenéz Á, Balasuriya UBR, Go YY. subsp. is the etiological agent of sleepy foal disease, an acute form of fatal septicemia in newborn foals. is commonly found in the mucous membranes of healthy horses' respiratory and alimentary tracts and rarely causes disease in adult horses. In this study, we report a case of a 22-year-old American Paint gelding presenting clinical signs associated with an atypical pattern of pleuropneumonia subjected to necropsy. The gross and histopathological examinations revealed a unilateral fibrinosuppurative and hemorrhagic pleuropneumonia with an infrequent parenchymal distribution and heavy iso...
Dobiáš R, Jahn P, Tóthová K, Dobešová O, Višňovská D, Patil R, Škríba A, Jaworská P, Škorič M, Podojil L, Kantorová M, Mrázek J....Invasive pulmonary aspergillosis (IPA) may be a rare cause of granulomatous pneumonia in horses. The mortality of IPA is almost 100%; direct diagnostic tools in horses are needed. Bronchoalveolar lavage fluid (BALF) and serum samples were collected from 18 horses, including individuals suffering from IPA (n = 1), equine asthma (EA, n = 12), and 5 healthy controls. Serum samples were collected from another 6 healthy controls. Samples of BALF (n = 18) were analyzed for spp. DNA, fungal galactomannan (GM), ferricrocin (Fc), triacetylfusarinin C (TafC), and gliotoxin (Gtx). Analysis of 24 serum s...
Tyma JF, Epstein KL.Sinusitis and pneumonia following exploratory celiotomy in horses were studied, evaluating associations between these 2 respiratory complications and selected pre-, peri-, and post-operative variables. The incidence of sinusitis was 2.5% (8/318) and pneumonia 3.5% (11/318). These respiratory complications were associated with peri-operative reflux, longer antimicrobial treatment, and longer hospitalization. . La sinusite et la pneumonie consécutives á une coeliotomie exploratoire chez le cheval ont été étudiées, afin d’évaluer les associations entre ces deux complications respiratoire...
Hassanpour A, Moghaddam S.Early detection of Rhodococcus equi pneumonia in foals is essential for horse health and for veterinarians. Objective: This study aimed to demonstrate the usefulness of assessing the serum concentration of acute-phase proteins (APPs) in the early diagnosis of pneumonia. Methods: The study evaluated APPs in 19 Arabian foals with R. equi pneumonia and compared them with 18 normal Arabian foals in equestrian clubs in Tabriz, Iran. Affected foals were identified through history, clinical findings and bacterial culture of tracheal washing. Biochemical methods and polymerase chain reaction tests wer...
Sanclemente JL, Rivera-Velez SM, Horohov DW, Dasgupta N, Sanz MG.Foals that develop pulmonary ultrasonographic lesions on Rhodococcus equi (R. equi) endemic farms are treated with antibiotics because those at risk of developing clinical pneumonia (~20%) cannot be recognised early. Candidate biomarkers identified using metabolomics may aid targeted treatment strategies against R. equi. Objective: (1) To describe how foal ageing affects their plasma metabolome (birth to 8 weeks) and (2) to establish the effects that experimental infection with Rhodococcus equi (R. equi) has on foal metabolome. Methods: Experimental study. Methods: Nine healthy newborn foals...
Hepworth-Warren KL, Nelson N, Dembek KA, Young KAS.Thoracic ultrasonography (TUS) is widely used in equine practice but comparison to radiography is limited in horses. Unassigned: To validate a novel, objective scoring system for TUS in adult horses and to compare ultrasonographic and radiographic findings. Unassigned: 13 healthy horses and 9 with confirmed bacterial pneumonia. Unassigned: Prospective study in which TUS and radiography were performed on healthy horses and those with bacterial pneumonia confirmed by clinical signs and results of transtracheal wash analysis. Ultrasonography was scored utilizing a novel scoring system evaluating ...
Manganiello CF, Basbus L, Callegari MS, Cayol F, Amaral De Sousa CR, Porta RE.Passive immunotherapy is a therapeutic alternative for patients with COVID-19. Methods: The decision was made to create a prospective database of patients diagnosed with SARS-CoV-2 pneumonia, nonhypoxemic, treated on an outpatient basis at the Hospital de Bolívar, Dr. Miguel Capredoni, province of Buenos Aires, Argentina, with the aim of evaluating the efficacy in reducing severe cases and hospitalizations of treatment with hyperimmune equine serum in this subgroup of patients. We performed a retrospective analysis of the period from 05/26/2021 to 08/28/2021, where a total of 151 patients wer...
Ahearne MM, Pentzke-Lemus LL, Romano AM, Larsen ED, Watson AM, O'Fallon EA, Landolt GA.Equine influenza virus is a common cause of respiratory disease in equids. Few reports describe clinical presentation and disease progression in donkeys. Objective: Describe the clinical and diagnostic findings, outcome, and pathologic lesions associated with influenza pneumonia in donkeys. Methods: Thirteen unvaccinated donkeys ranging from 1 week to 12 years of age and sharing clinical signs and exposure history. Methods: Retrospective case series. Medical records from June to July 2020 at the Colorado State Veterinary Teaching Hospital and collaborating referring veterinary practices wer...
Begg AP, Carrick J, Chicken C, Blishen A, Todhunter K, Eamens K, Jenkins C.This report describes the fetoplacental pathology of associated abortion, premature birth, and neonatal loss in 46 of 442 equine abortion investigations between 2015 and 2019. Seven abortions, 26 premature births, and 13 neonatal deaths with positive polymerase chain reaction (PCR) were evaluated. In 83% of cases (38/46), infection was considered as the primary cause of loss based on quantitative PCR (qPCR) confirmation, pathological findings, and exclusion of other causes, and was supported by immunolabeling in fetoplacental lesions. Lymphohistiocytic placentitis with vasculitis (36/38) af...
Xu Z, Hao X, Li M, Luo H.Rhodococcus equi (R. equi) is a Gram-positive coccobacillus that causes pneumonia in foals of less than 3 months, which have the ability of replication in macrophages. The ability of R. equi persist in macrophages is dependent on the virulence plasmid pVAPA. Gram-positive extracellular vesicles (EVs) carry a variety of virulence factors and play an important role in pathogenic infection. There are few studies on R. equi-derived EVs (R. equi-EVs), and little knowledge regarding the mechanisms of how R. equi-EVs communicate with the host cell. In this study, we examine the properties of EVs prod...
Kahn SK, Cohen ND, Bordin AI, Coleman MC, Heird JC, Welsh TH.The bacterium Rhodococcus equi causes pneumonia in foals that is prevalent at breeding farms worldwide. In the absence of an effective vaccine, transfusion of commercial plasma from donor horses hyperimmunised against R. equi is used by many farms to reduce the incidence of pneumonia among foals at farms where the disease is endemic. The effectiveness of hyperimmune plasma for controlling R. equi pneumonia in foals has varied considerably among reports. The purposes of this narrative review are: (1) to review early studies that provided a foundational basis for the practice of transfusion of h...
Macías-Rioseco M, Sheley M, Ochoa J, Carvallo-Chaigneau FR, Uzal FA.Coccidioidomycosis is a fungal disease caused by or . We searched the records of the California Animal Health and Food Safety Laboratory from 1990 through 2020 for cases of coccidioidomycosis in horses. The selection criteria for these cases were: 1) live-born horses submitted for autopsy, and 2) a diagnosis of coccidioidomycosis was established, regardless of cause of death. During that time, 19,054 horses were received, and 26 cases (0.14%) of coccidioidomycosis were diagnosed in horses, of which 19 (73%) cases had pneumonia and/or pleuritis with or without lesions in other organs, and 7 (2...
Prescott JF.Recent isolations of Rhodococcus equi from cavitatory pulmonary disease in patients with AIDS have aroused interest among medical microbiologists in this unusual organism. Earlier isolations from humans had also been in immunosuppressed patients following hemolymphatic tumors or renal transplantation. This organism has been recognized for many years as a cause of a serious pyogranulomatous pneumonia of young foals and is occasionally isolated from granulomatous lesions in several other species, in some cases following immunosuppression. The last decade has seen many advances in understanding o...
Lykkesfeldt J, Svendsen O.Important infectious diseases in farm animals, such as pneumonia and enteritis, are thought to be associated with the so-called oxidative stress, i.e. a chemical phenomenon involving an imbalance in the redox status of the individual animal. The specifics of oxidative stress and how it may result in disease or be prevented are complex questions with no simple answers. However, the considerable literature on the subject suggests that many researchers consider oxidative stress-related mechanisms to be important early events in disease development. A particularly intriguing aspect is that, at lea...
Hondalus MK, Mosser DM.Rhodococcus equi is a facultative intracellular bacterium of macrophages that can cause serious pneumonia in both young horses and immunocompromised people. Essential to understanding rhodococcus pathogenesis is a quantitative documentation of the intracellular events that follow macrophage phagocytosis of the organism. By using a bacterial immunofluorescence staining assay, we verified the intracellular survival and replicative potential of R. equi in both murine peritoneal macrophages and equine alveolar macrophages in vitro. Following an initial lag period of 6 to 12 h, the intracellular nu...
Giguère S, Cohen ND, Chaffin MK, Hines SA, Hondalus MK, Prescott JF, Slovis NM.Pneumonia is a major cause of disease and death in foals. Rhodococcus equi, a gram-positive facultative intracellular pathogen, is a common cause of pneumonia in foals. This article reviews the clinical manifestations of infection caused by R. equi in foals and summarizes current knowledge regarding mechanisms of virulence of, and immunity to, R. equi. A complementary consensus statement providing recommendations for the diagnosis, treatment, control, and prevention of infections caused by R. equi in foals can be found in the same issue of the Journal.
Meijer WG, Prescott JF.Rhodococcus equi is an important cause of subacute or chronic abscessating bronchopneumonia of foals up to 3-5 months of age. It shares the lipid-rich cell wall envelope characteristic of the mycolata, including Mycobacterium tuberculosis, as well as the ability of pathogenic members of this group to survive within macrophages. The possession of a large virulence plasmid in isolates recovered from pneumonic foals is crucial for virulence. The plasmid contains an 27 kb pathogenicity island (PI) that encodes seven related virulence-associated proteins (Vaps), including the immunodominant surface...
Giguère S, Cohen ND, Chaffin MK, Slovis NM, Hondalus MK, Hines SA, Prescott JF.Rhodococcus equi, a gram-positive facultative intracellular pathogen, is one of the most common causes of pneumonia in foals. Although R. equi can be cultured from the environment of virtually all horse farms, the clinical disease in foals is endemic at some farms, sporadic at others, and unrecognized at many. On farms where the disease is endemic, costs associated with morbidity and mortality attributable to R. equi may be very high. The purpose of this consensus statement is to provide recommendations regarding the diagnosis, treatment, control, and prevention of infections caused by R. equi...
van der Geize R, Grommen AW, Hessels GI, Jacobs AA, Dijkhuizen L.Rhodococcus equi causes fatal pyogranulomatous pneumonia in foals and immunocompromised animals and humans. Despite its importance, there is currently no effective vaccine against the disease. The actinobacteria R. equi and the human pathogen Mycobacterium tuberculosis are related, and both cause pulmonary diseases. Recently, we have shown that essential steps in the cholesterol catabolic pathway are involved in the pathogenicity of M. tuberculosis. Bioinformatic analysis revealed the presence of a similar cholesterol catabolic gene cluster in R. equi. Orthologs of predicted M. tuberculosis vi...
Cohen ND.A prospective study was conducted to describe the causes of and farm management factors associated with disease and death in a population of foals in Texas. Data from 2,468 foals at 167 farms were provided by veterinarians for all 12 months during 1991. Among 2,468 foals, 116 deaths were reported (4.7%). Pneumonia was the most commonly reported cause of death, followed by septicemia. When considered as a group, musculoskeletal disorders (traumatic, infectious, or deforming problems) represented the most common cause of all reported deaths. Daily risk of death was greatest during the first 7 da...
Byrne BA, Prescott JF, Palmer GH, Takai S, Nicholson VM, Alperin DC, Hines SA.Rhodococcus equi causes severe pyogranulomatous pneumonia in foals. This facultative intracellular pathogen produces similar lesions in immunocompromised humans, particularly in AIDS patients. Virulent strains of R. equi bear a large plasmid that is required for intracellular survival within macrophages and for virulence in foals and mice. Only two plasmid-encoded proteins have been described previously; a 15- to 17-kDa surface protein designated virulence-associated protein A (VapA) and an antigenically related 20-kDa protein (herein designated VapB). These two proteins are not expressed by t...
Giguère S, Lee E, Williams E, Cohen ND, Chaffin MK, Halbert N, Martens RJ, Franklin RP, Clark CC, Slovis NM.To determine the prevalence of antimicrobial resistance to macrolide antimicrobials or rifampin in Rhodococcus equi isolates and to describe treatment outcome in foals infected with antimicrobial-resistant isolates of R equi. Methods: Cross-sectional study. Methods: 38 isolates classified as resistant to macrolide antimicrobials or rifampin received from 9 veterinary diagnostic laboratories between January 1997 and December 2008. Methods: For each isolate, the minimum inhibitory concentration of macrolide antimicrobials (ie, azithromycin, erythromycin, and clarithromycin) and rifampin was dete...
Ashour J, Hondalus MK.Rhodococcus equi is a facultative intracellular opportunistic pathogen of immunocompromised people and a major cause of pneumonia in young horses. An effective live attenuated vaccine would be extremely useful in the prevention of R. equi disease in horses. Toward that end, we have developed an efficient transposon mutagenesis system that makes use of a Himar1 minitransposon delivered by a conditionally replicating plasmid for construction of R. equi mutants. We show that Himar1 transposition in R. equi is random and needs no apparent consensus sequence beyond the required TA dinucleotide. The...
Yager JA.The pathogenesis of Rhodococcus equi pneumonia in foals is reviewed. The main routes of infection are respiratory and alimentary. The latter is probably the chief route of exposure in all foals and probably leads to development of specific immunity. Susceptible foals, those whose maternal immunity wanes before generation of their own immune response, readily develop disease if exposed aerogenously to sufficient numbers of R. equi. Management and environmental circumstances have a major role to play in determining the magnitude of this challenge and, therefore, in the prevalence of the disease....
Martens RJ, Martens JG, Fiske RA, Hietala SK.The immunoprophylactic capacity of specific immune plasma was evaluated in pony foals infected experimentally with Rhodococcus equi. Immune plasma, produced by repeated parenteral administration of viable R. equi to adult horses, was harvested and frozen. Group I (six control foals) and Group II (six principal foals) received lactated Ringers solution and immune plasma respectively at three and five days of age. R. equi were aerosolised into a caudal lung lobe of all foals at seven days of age. Clinical signs, haematological alterations, immune responses, thoracic radiographs and technetium99m...
Venner M, Rödiger A, Laemmer M, Giguère S.Mass antimicrobial treatment of foals with small ultrasonographic pulmonary lesions is common on farms with endemic disease caused by Rhodococcus equi. The objectives of this study were to compare the relative efficacy of three antimicrobial protocols for the treatment of pulmonary abscesses on a farm with endemic infections caused by R. equi and to determine the frequency of spontaneous resolution of subclinical pulmonary lesions. Foals with ultrasonographic evidence of pulmonary abscesses ≥ 1.0 cm in diameter (n=128) were randomly allocated to one of four equal treatment groups. Animals wi...
Kanaly ST, Hines SA, Palmer GH.Rhodococcus equi, a facultative intracellular bacterium, causes chronic, often fatal granulomatous pneumonia in young horses and in humans with AIDS. The inability of host alveolar macrophages to kill intracellular R. equi results in the development of granulomas and progressive loss of pulmonary parenchyma. Clearance of the organism from the lung requires functional CD4+ T cells. The purpose of this study was to identify the cytokine effector mechanisms that mediate clearance of R. equi from the lung. Mice were treated with monoclonal antibodies (MAbs) to either gamma interferon (IFN-gamma) o...
Lopez AM, Hines MT, Palmer GH, Alperin DC, Hines SA.Rhodococcus equi infects and causes pneumonia in foals between 2 and 4 months of age but does not induce disease in immunocompetent adults, which are immune and remain clinically normal upon challenge. Understanding the protective response against R. equi in adult horses is important in the development of vaccine strategies, since those mechanisms likely reflect the protective phenotype that an effective vaccine would generate in the foal. Twelve adult horses were challenged with virulent R. equi and shown to be protected against clinical disease. Stimulation of cells obtained from bronchoalve...
Hooper PT, Ketterer PJ, Hyatt AD, Russell GM.Laboratory examinations of equine morbillivirus included experimental reproductions of the disease caused by the virus by transmission of mixed lung and spleen taken from two field equine cases into two horses and by inoculating tissue culture virus into a further two horses. The most distinctive gross lesions of the diseases that developed in three of the horses was that of pulmonary edema characterized by gelatinous distension of subpleural lymphatics. Histologically, the lesions in the lungs were those of serofibrinous alveolar edema, alveolar macrophages, hemorrhage, thrombosis of capillar...
Wada R, Kamada M, Anzai T, Nakanishi A, Kanemaru T, Takai S, Tsubaki S.Twelve foals, between 27 and 83 days old, were infected with 2 strains of Rhodococcus equi by intratracheal administration. Ten of the 12 foals were inoculated with 10(4)-10(10) colony forming units (cfu) of ATCC 33701 strain. The other 2 foals were inoculated with 10(9) cfu of a plasmid-cured derivative of the ATCC 33701 strain (ATCC 33701P-). All of the 10 foals challenged with the ATCC 33701 strain showed clinical signs of pulmonary disease within 5-13 days, such as gross lesions associated with acute bronchopneumonia and microscopic lesions associated with granulomatous pneumonia. The two ...
Muscatello G, Anderson GA, Gilkerson JR, Browning GF.The ecology of virulent strains of Rhodococcus equi on horse farms is likely to influence the prevalence and severity of R. equi pneumonia in foals. This study examined the association between the ecology of virulent R. equi and the epidemiology of R. equi pneumonia by collecting air and soil samples over two breeding seasons (28 farm-year combinations) on Thoroughbred breeding farms with different reported prevalences of R. equi pneumonia. Colony blotting and DNA hybridization were used to detect and measure concentrations of virulent R. equi. The prevalence of R. equi pneumonia was associate...
Padalino B, Raidal SL, Hall E, Knight P, Celi P, Jeffcott L, Muscatello G.An online survey was conducted to determine associations between transport management and transport-related injuries and diseases in horses in Australia. The survey was composed of three sections: respondents' demographic information, transport management strategies or procedures (before, during and after transportation) and transport diseases experienced in the previous two year period. Univariate and multivariate modelling was performed exploring associations between variables (respondents' details and transport management strategies) and the following transport-related diseases as outcomes:...
Vo AT, van Duijkeren E, Fluit AC, Gaastra W.The aim of the present study was to contribute to the knowledge on extended-spectrum beta-lactamases (ESBL's), AmpC beta-lactamases and integrons in Enterobacteriaceae isolated from horses, which is still limited. The susceptibility of 1581 clinical isolates from animals to ceftiofur was tested. Most of these isolates (n=1347) originated from horses. Seven ceftiofur-resistant equine isolates (four Escherichia coli and three Klebsiella pneumoniae) were identified and all seven were multidrug-resistant. These isolates were further studied for the presence of ESBL's, AmpC beta-lactamases and clas...
Hobo S, Niwa H, Anzai T.In the present study, the concentrations of serum amyloid A and surfactant protein D in sera were measured to evaluate them for identification of the clinical condition of horses with bacterial pneumonia. The study utilized 185 clinically healthy control thoroughbreds and 9 thoroughbreds for experimental infectious study with S. zooepidemicus. Blood samples were collected from the 185 healthy control thoroughbreds. The 9 thoroughbreds were experimentally infected S. zooepidemicus using an endoscopic injection to a lung lobe and were then observed of clinical conditions. Blood samples were coll...
Dei-Cas E, Brun-Pascaud M, Bille-Hansen V, Allaert A, Aliouat EM.As in vitro culture systems allowing to isolate Pneumocystis samples from patients or other mammal hosts are still not available, animal models have critical importance in Pneumocystis research. The parasite was reported in numerous mammals but P. carinii pneumonia (PCP) experimental models were essentially developed by using rats, mice, rabbits and ferrets. The rat treated with corticosteroids for 9-12 weeks is a useful PCP model. Like laboratory rats, conventional mice develop PCP after prolonged corticosteroid administration. The ferret (Mustela putorius furo) also develop PCP under cortico...
Padalino B, Raidal SL, Knight P, Celi P, Jeffcott L, Muscatello G.This study aimed to document the effects of an eight hour journey on behavioural, clinical, haematological, environmental and respiratory parameters, and to identify possible associations between factors. Twelve horses underwent clinical examination, respiratory endoscopy with tracheal wash (TW) aspiration, and collection of venous and arterial blood before (BJ) and after the journey (AJ). TW were submitted for conventional quantitative bacteriological evaluation and genetic microbiome analyses. Behaviour was assessed in stables prior to transportation and throughout the journey. Transportatio...
Hines SA, Stone DM, Hines MT, Alperin DC, Knowles DP, Norton LK, Hamilton MJ, Davis WC, McGuire TC.Rhodococcus equi is a gram-positive bacterium that infects alveolar macrophages and causes rhodococcal pneumonia in horses and humans. The virulence plasmid of R. equi appears to be required for both pathogenicity in the horse and the induction of protective immunity. An understanding of the mechanisms by which virulent R. equi circumvents protective host responses and by which bacteria are ultimately cleared is important for development of an effective vaccine. Six adult horses were challenged with either virulent R. equi or an avirulent, plasmid-cured derivative. By using a flow cytometric m...
Giguère S, Gaskin JM, Miller C, Bowman JL.To determine efficacy of a commercially available hyperimmune plasma product for prevention of naturally acquired pneumonia caused by Rhodococcus equi in foals. Methods: Randomized clinical trial. Methods: 165 foals. Methods: Foals were randomly assigned to 1 of 2 groups (hyperimmune plasma or nontreated controls). Foals with failure of passive transfer (FPT) of immunity were treated with hyperimmune plasma and evaluated as a third group. Foals that received plasma were given 950 ml between 1 and 10 days of age and between 30 and 50 days of age. A tracheobronchial aspirate was obtained from fo...
Whatmore AM, King SJ, Doherty NC, Sturgeon D, Chanter N, Dowson CG.Although often considered a strict human pathogen, Streptococcus pneumoniae has been reported to infect and cause pneumonia in horses, although the pathology appears restricted compared to that of human infections. Here we report on the molecular characterization of a group of S. pneumoniae isolates obtained from horses in England and Ireland. Despite being obtained from geographically distinct locations, the isolates were found to represent a tight clonal group, virtually identical to each other but genetically distinguishable from more than 120 divergent isolates of human S. pneumoniae. A co...
Álvarez-Narváez S, Berghaus LJ, Morris ERA, Willingham-Lane JM, Slovis NM, Giguere S, Cohen ND.The practice of prophylactic administration of a macrolide antimicrobial with rifampin (MaR) to apparently healthy foals with pulmonary lesions identified by thoracic ultrasonography (i.e., subclinically pneumonic foals) is common in the United States. The practice has been associated epidemiologically with emergence of R. equi resistant to MaR. Here, we report direct evidence of multi-drug resistance among foals treated with MaR. In silico and in vitro analysis of the fecal microbiome and resistome of 38 subclinically pneumonic foals treated with either MaR (n = 19) or gallium maltolate (...
