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Topic:Asymptomatic Carriers

Asymptomatic carriers are horses that harbor infectious agents without displaying clinical signs of disease. These carriers can shed pathogens into the environment, potentially transmitting infections to other animals. Understanding the role of asymptomatic carriers is important for managing disease spread within equine populations. Research in this area focuses on identifying specific pathogens that can be carried asymptomatically, the duration and conditions of carriage, and the implications for herd health management. This page aggregates peer-reviewed research studies and scholarly articles that explore the identification, epidemiology, and impact of asymptomatic carriers in equine health.
Horses seropositive for Toxoplasma gondii, Sarcocystis spp. and Neospora spp.: Possible risk factors for infection in Brazil.
Microbial pathogenesis    July 27, 2016   Volume 99 30-35 doi: 10.1016/j.micpath.2016.07.016
Cazarotto CJ, Balzan A, Grosskopf RK, Boito JP, Portella LP, Vogel FF, Fávero JF, de C Cucco D, Biazus AH, Machado G, Da Silva AS.Many parasitic diseases are considered asymptomatic, even though some studies have shown that they may cause pathological changes in the host. Therefore, the aim of this study was to evaluate the occurrence of antibodies against Toxoplasma gondii, Neospora spp. and Sarcocystis spp. in horses, and to identify the risk factors for disease. For this, 174 horses were studied, 90 males and 84 females aged between two and 20 years old. Blood samples were collected and stored in tubes without anticoagulant to obtain serum, which was subjected to serological tests for T. gondii, Sarcocystis spp., and...
Serosurvey Reveals Exposure to West Nile Virus in Asymptomatic Horse Populations in Central Spain Prior to Recent Disease Foci.
Transboundary and emerging diseases    May 8, 2016   Volume 64, Issue 5 1387-1392 doi: 10.1111/tbed.12510
Abad-Cobo A, Llorente F, Barbero MDC, Cruz-López F, Forés P, Jiménez-Clavero MÁ.West Nile fever/encephalitis (WNF) is an infectious disease affecting horses, birds and humans, with a cycle involving birds as natural reservoirs and mosquitoes as transmission vectors. It is a notifiable disease, re-emerging in Europe. In Spain, it first appeared in horses in the south (Andalusia) in 2010, where outbreaks occur every year since. However, in 2014, an outbreak was declared in horses in central Spain, approximately 200 km away from the closest foci in Andalusia. Before that, evidence of West Nile virus (WNV) circulation in central Spain had been obtained only from wildlife, bu...
Molecular Detection of Equine Herpesvirus Types 1 and 4 Infection in Healthy Horses in Isfahan Central and Shahrekord Southwest Regions, Iran.
BioMed research international    September 1, 2015   Volume 2015 917854 doi: 10.1155/2015/917854
Taktaz Hafshejani T, Nekoei S, Vazirian B, Doosti A, Khamesipour F, Anyanwu MU.This study was undertaken to investigate molecularly the occurrence of EHV-1 and EHV-4 infection among equine population in regions, Iran. Blood samples from 53 and 37 randomly selected horses settled in Isfahan and Shahrekord, Iran, respectively, were collected. Detection of EHV-1 and EHV-4 genes in the blood samples was done using polymerase chain reaction (PCR). Out of 53 and 37 samples from Isfahan and Shahrekord, 4 (18.18%) and 3 (8.10%) were positive for PCR of EHV-1, respectively. Nine (16.98%) and 6 (16.21%) were positive for PCR of EHV-4, while 6 (11.32%) and 3 (8.10%) were positive f...
High seroprevelance of West Nile virus antibodies observed in horses from southwestern Nigeria.
Vector borne and zoonotic diseases (Larchmont, N.Y.)    March 21, 2015   Volume 15, Issue 3 218-220 doi: 10.1089/vbz.2014.1706
Sule WF, Oluwayelu DO, Adedokun RA, Rufai N, McCracken F, Mansfield KL, Johnson N.To investigate exposure of Nigerian horses to West Nile virus (WNV), we determined the seroprevalence rate of anti-WNV antibody in a cohort of 145 horses. Serum samples were collected from three locations in southwestern Nigeria between October, 2011, and July, 2012. The horses were asymptomatic and unvaccinated against WNV at the time of sampling. All sera were tested using a competition enzyme-linked immmunosorbent assay (ELISA) and by an immunoglobulin M (IgM)-specific ELISA. High rates of anti-WNV antibody prevalence were observed in all locations with a mean level of 90.3% (95% confidence...
Gross and Histopathologic Correlation of Low-Field Magnetic Resonance Imaging Findings in the Stifle of Asymptomatic Horses. Santos MP, Gutierrez-Nibeyro SD, McKnight AL, Singh K.With the recent introduction of a 0.25T rotating MRI system, clinical evaluation of the equine stifle joint is now possible in the average equine athlete. A recent publication described common abnormalities of horses with stifle lameness detected with a low-field MRI system; however, postmortem corroboration of the lesions detected was not possible. Therefore, our objective was to compare postmortem findings with low-field MRI findings in equine cadaver stifle joints. Ten fresh cadaver stifle joints from horses without clinical signs of stifle disease were evaluated using low-field MRI, gross ...
Piroplasmosis in an endemic area: analysis of the risk factors and their implications in the control of Theileriosis and Babesiosis in horses.
Parasitology research    October 4, 2014   Volume 114, Issue 1 71-83 doi: 10.1007/s00436-014-4161-9
Guidi E, Pradier S, Lebert I, Leblond A.Theileria equi (Laveran 1901) and Babesia caballi (Nuttall and Strickland 1910) are the causative agents of Equine Piroplasmosis (EP), a severe and problematic disease compromising international movement of horses. Infected horses usually become asymptomatic carriers and, for this reason, their movement across borders may become restricted. The aim of this study was to assess the seroprevalence of EP in Southern France and to evaluate risk factors associated with these parasites. In 2002, we performed a complement fixation test (CF) with blood samples from 443 horses stabled at 95 different fa...
Gastrointestinal ultrasonography of normal Standardbred neonates and frequency of asymptomatic intussusceptions.
Journal of veterinary internal medicine    August 7, 2014   Volume 28, Issue 5 1580-1586 doi: 10.1111/jvim.12413
Abraham M, Reef VB, Sweeney RW, Navas de Solís C.Ultrasonographic appearance of the gastrointestinal (GI) tract of equine neonates has not been completely described. Objective: To describe (1) sonographic characteristics of the GI segments in normal nonsedated equine neonates, (2) intra- and interobserver variation in wall thickness, and (3) the sonographic appearance of asymptomatic intussusceptions, and (4) to compare age and sonographic findings of foals with and without asymptomatic intussusceptions. Methods: Eighteen healthy Standardbred foals ≤5 days of age. Methods: Prospective, cross-sectional blinded study. Gastrointestinal sonogr...
Glutamate and lipid metabolic perturbation in the hippocampi of asymptomatic borna disease virus-infected horses.
PloS one    June 23, 2014   Volume 9, Issue 6 e99752 doi: 10.1371/journal.pone.0099752
Zhang L, Lei Y, Liu X, Wang X, Liu Z, Li D, Zheng P, Zhang L, Chen S, Xie P.Borna disease virus (BDV) is a neurotropic, enveloped, non-segmented, negative-stranded RNA virus that infects a wide variety of vertebrate species from birds to humans across a broad global geographic distribution. Animal symptomatology range from asymptomatic infection to behavioral abnormalities to acute meningoencephalitis. Asymptomatic BDV infection has been shown to be more frequent than conventionally estimated. However, the molecular mechanism(s) underyling asymptomatic BDV infection remain largely unknown. Here, based on real-time quantitative PCR and Western blotting, a total of 18 h...
Diagnosis of subclinical equine theileriosis in center of Iran using parasitological and molecular methods.
Tropical biomedicine    May 28, 2014   Volume 31, Issue 1 110-117 
Bahrami S, Ghadrdan AR, Mirabdollahi SM, Fayed MR.A total of 105 blood samples from healthy horses from different stables in Yazd province, center of Iran, were examined for the presence of Theileria equi infection using parasitological and molecular methods. Out of the 105 samples, the parasitological method detected T. equi infection in 5 (4.76%) cases while the PCR method gave 24 (22.86%) positive results. Age, gender and breed were not determined as risk factors for T. equi infection in this study. Since blood samples were taken from healthy animals, this implies that 22.86% of horses had subclinical theileriosis in the current study. In ...
Can Theileria equi be eliminated from carrier horses?
Veterinary journal (London, England : 1997)    June 2, 2013   Volume 196, Issue 3 279 doi: 10.1016/j.tvjl.2013.03.016
Butler C.No abstract available
Yeast-like fungi and yeasts isolated from healthy breeding horses.
Polish journal of veterinary sciences    May 23, 2013   Volume 16, Issue 1 69-76 
Pacyńska JA.Horses are characterized by a very high incidence of mycoses in comparison with most livestock and companion animals. They are highly susceptible to asymptomatic infections caused by yeast-like fungi, but the carrier state may be disrupted under the influence of autogenic and allogenic factors. The above leads to severe organ mycoses, often with an acute form of infection. "Carrier horses" may also act as vectors which transmit potential pathogens between individuals and species. The aim of this study was to identify yeast-like fungi and yeast colonizing the ontocenoses of healthy horses and t...
Detection of Theileria equi in spleen and blood of asymptomatic piroplasm carrier horses.
Acta parasitologica    May 11, 2013   Volume 58, Issue 2 218-222 doi: 10.2478/s11686-013-0127-9
Ribeiro IB, Câmara AC, Bittencourt MV, Marçola TG, Paludo GR, Soto-Blanco B.This study aimed to determine whether asymptomatic horses naturally infected with Theileria equi retain infected erythrocytes in the spleen and whether the presence of the hemoparasite in this organ is associated with parasitemia. We collected samples from 25 adult horses without clinical signs of any disease. From each animal, we collected whole blood samples from the jugular vein and a splenic puncture blood sample. All samples were submited to blood cell counts and detection of Theileria or Babesia. DNA extraction and PCR were performed in all samples for identification of piroplasm infecti...
Identification of piroplasms isolated from asymptomatic equine species from southern Spain.
Berliner und Munchener tierarztliche Wochenschrift    December 12, 2012   Volume 125, Issue 11-12 509-512 
Adaszek Ł, García-Bocanegra I, Arenas-Montes A, Carbonero A, Arenas A, Winiarczyk S.The aim of the study was to detect the presence of genetic material of equine piroplasmas and to determine the species isolates from apparently healthy equids, including horses, donkeys and mules, in southern Spain. Blood samples were collected from 135 animals to assess the presence of DNA from equine piroplasmas using PCR. Babesia (B.) caballi DNA was detected in blood samples of three horses and one donkey, while Theileria (T.) equi DNA was confirmed in blood of 19 horses, three mules and one donkey. All B. caballi isolates showed a 100% homology of the nucleotide sequence of the 18S RNA ge...
Clonal transmission of a rare methicillin-resistant Staphylococcus aureus genotype between horses and staff at a veterinary teaching hospital.
Veterinary microbiology    November 26, 2012   Volume 162, Issue 2-4 907-911 doi: 10.1016/j.vetmic.2012.11.020
Schwaber MJ, Navon-Venezia S, Masarwa S, Tirosh-Levy S, Adler A, Chmelnitsky I, Carmeli Y, Klement E, Steinman A.Methicillin-resistant Staphylococcus aureus (MRSA) infection or colonization has become a serious emerging condition in equine hospitals. Following the detection of MRSA in asymptomatic hospitalized horses and in two horses with post-operative wound infections, an investigation was conducted. Twelve of 84 horses (14.3%) and 16 of 139 personnel (11.5%) were MRSA carriers. The profile of the dominant MRSA strain common to horses and staff was multi-drug-resistant, spa-type t535, SCCmec type V, pvl-negative. MLST of a representative isolate yielded sequence type (ST) 5. The risk of MRSA carriage ...
PCR detection of leptospiral carriers among seronegative horses.
The Veterinary record    July 31, 2012   Volume 171, Issue 4 105-106 doi: 10.1136/vr.e5022
Hamond C, Martins G, Lilenbaum W, Medeiros MA.No abstract available
Transmission of Lawsonia intracellularis to weanling foals using feces from experimentally infected rabbits.
Veterinary journal (London, England : 1997)    July 28, 2012   Volume 195, Issue 2 241-243 doi: 10.1016/j.tvjl.2012.05.028
Pusterla N, Sanchez-Migallon Guzman D, Vannucci FA, Mapes S, White A, DiFrancesco M, Gebhart C.The aim of this study was to investigate whether feces from rabbits experimentally infected with Lawsonia intracellularis were infectious to foals. Two rabbits were infected with L. intracellularis, while two rabbits served as controls. Eight foals received daily feces from either the infected or the control rabbits. All rabbits and foals were monitored daily for clinical signs for the entire study period (21days for rabbits, 42days for foals). Feces and blood were collected for the PCR detection of L. intracellularis and serologic analysis, respectively. None of the infected rabbits or foals ...
Presence and molecular characterization of Clostridium difficile and Clostridium perfringens in intestinal compartments of healthy horses.
BMC veterinary research    June 29, 2012   Volume 8 94 doi: 10.1186/1746-6148-8-94
Schoster A, Arroyo LG, Staempfli HR, Shewen PE, Weese JS.Clostridium difficile and Clostridium perfringens are commonly associated with colitis in equids, but healthy carriers exist. Scarce information is available on the prevalence of Clostridium spp. in gastrointestinal compartments other than faeces in healthy horses, and it is unknown whether faecal samples are representative of proximal compartments. The objectives were to investigate the prevalence of C. difficile and C. perfringens in different intestinal compartments of healthy adult horses and to determine whether faecal samples are representative of colonization in proximal sites and overa...
Seroepidemiological survey of Rhodococcus equi infection in asymptomatic horses and donkeys from southeast Turkey.
Journal of the South African Veterinary Association    May 24, 2012   Volume 82, Issue 4 224-226 doi: 10.4102/jsava.v82i4.78
Tel OY, Arserim NB, Keskin O.In order to assess the level of Rhodococcus equi infection in southeast Turkey, 679 sera from healthy foals and adult horses and 78 sera from donkeys were tested by indirect ELISA using a R. equi reference strain (ATCC 33701) as antigen. Eighty (11.7%) sera from horses and 9 (11.5%) sera from donkeys with titres >0.85 were positive. The prevalence of seropositive horses in Sanliurfa Province was higher than in Diyarbakir Province; 56 (13.9%) horses in Sanliurfa Province and 24 (8.7%) horses in Diyarbakir Province were defined as seropositive. In Sanliurfa Province 14.5% of female (n=343) an...
Prevalence of Trypanosoma evansi in horses in Israel evaluated by serology and reverse dot blot.
Research in veterinary science    May 11, 2012   Volume 93, Issue 3 1225-1230 doi: 10.1016/j.rvsc.2012.04.009
Berlin D, Nasereddin A, Azmi K, Ereqat S, Abdeen Z, Eyal O, Baneth G.Trypanosoma evansi is the cause of surra in horses, camels and other domestic animals. Following the first outbreak of surra in horses and camels in Israel in 2006, a survey of the prevalence of the parasite in the Israeli horse population was conducted using serology, PCR followed by the reverse dot blot (RDB) technique and blood smear microscopy. In total, 614 horses from 7 regions were sampled. The CATT/T. evansi kit was used for serology for all the horses. Horses from the Arava and Dead Sea region, where the first outbreak occurred, were sampled again one year later and both samples were ...
Synovial fluid chondroitin sulphate indicates abnormal joint metabolism in asymptomatic osteochondritic horses.
Equine veterinary journal    January 19, 2012   Volume 44, Issue 4 404-411 doi: 10.1111/j.2042-3306.2011.00539.x
Machado TS, Correia da Silva LC, Baccarin RY, Michelacci YM.Alternative methods to evaluate the joint condition in asymptomatic osteochondrosis dissecans (OCD) and other joint diseases may be useful. Objective: To investigate possible changes in synovial fluid composition that may lead to joint conditions in asymptomatic OCD, in mature horses. Methods: Animals aged >2 years, of different breeds, with OCD in the intermediate ridge of distal tibia, symptomatic or not, were studied. Synovial fluid samples (10 healthy; 11 asymptomatic OCD; 25 symptomatic OCD) were collected by arthroscopy from 29 horses. Glycosaminoglycans (GAGs) were analysed by a comb...
[Serological study carried out in Cuban localities where confirmed western Nile virus infection is present].
Revista cubana de medicina tropical    September 1, 2011   Volume 63, Issue 3 227-230 
first infected cases caused by West Nile virus were reported in Cuba in 2004. Objective: to monitor and learn about the prevalence of the West Nile virus in those areas with confirmed cases. Methods: the study was conducted in Jatibonico municipality and in the city of sancti Spiritus. A total number of 14 persons, 8 horses and 41 birds were researched to detect antibodies to flavivirus and specific antibodies to West Nile virus. Results: the presence of specific antibodies to West Nile virus was confirmed in 4 samples of sera from birds and in 4 from horses. One person was confirmed as one ca...
Streptococcus equi: a pathogen restricted to one host.
Journal of medical microbiology    July 14, 2011   Volume 60, Issue Pt 9 1231-1240 doi: 10.1099/jmm.0.028233-0
Waller AS, Paillot R, Timoney JF.Strangles caused by the host adapted Lancefield group C Streptococcus equi subspecies equi (S. equi) is a frequently diagnosed infectious disease of horses worldwide. Critical to the global success of S. equi is its ability to establish persistent infections within the guttural pouches of recovered apparently healthy horses that can result in transmission to in-contact animals. Recent research has identified key events in the S. equi genome, which occurred during its evolution from an ancestral strain of S. equi subspecies zooepidemicus, that may enhance its ability to evade host innate immune...
Longitudinal study of an outbreak of Trypanosoma evansi infection in equids and dromedary camels in Israel.
Veterinary parasitology    September 15, 2010   Volume 174, Issue 3-4 317-322 doi: 10.1016/j.vetpar.2010.09.002
Berlin D, Nasereddin A, Azmi K, Ereqat S, Abdeen Z, Baneth G.An outbreak of trypanosomoasis caused by Trypanosoma evansi involving horses, camels and donkeys occurred in a farm in Israel. A longitudinal study of two outbreak phases was conducted which included clinical monitoring, blood smears, packed cell volume (PCV), serology and polymerase chain reaction (PCR) followed by reverse dot blot (RDB) for the molecular detection of infection. This was the first reported T. evansi outbreak in domestic animals in Israel. Most of the camels on the farm (8/10; 80%) were diagnosed with T. evansi infection whereas infection was less prevalent in the horses (3/7;...
[MRSA-positive horses are not necessarily carriers].
Tijdschrift voor diergeneeskunde    September 9, 2010   Volume 135, Issue 16 608-610 
Haneveld JK.No abstract available
Serosurveillance for equine infectious anaemia in the Ardahan province of Turkey.
Tropical animal health and production    June 3, 2010   Volume 42, Issue 8 1593-1595 doi: 10.1007/s11250-010-9611-5
Albayrak H, Ozan E.Equine infectious anaemia is a retroviral infection of horses. All infected horses, including those that are asymptomatic, become carriers and are infectious for life. In this study, blood samples of all equines in the province of Ardahan were collected. The material consisted of 8,947 equines, including 8,769 horses and 178 donkeys, from Ardahan province in northeastern Turkey. Blood was collected from all horses and donkeys and the sera were analysed for the presence of antibodies to equine infectious anaemia virus (EIAV) using an enzyme-linked immunosorbent assay. The results revealed that ...
Subclinical infection and periodic shedding of equid herpesvirus 3.
Theriogenology    May 23, 2010   Volume 74, Issue 4 576-580 doi: 10.1016/j.theriogenology.2010.03.014
Barrandeguy M, Vissani A, Lezica FP, Salamone J, Heguy A, Becerra L, Olguin Perglione C, Thiry E.The temporary disruption of reproductive activities due to equine coital exanthema (ECE), caused by equid herpesvirus 3 (EHV-3), at thoroughbred breeding facilities and embryo transfer centres, has an appreciable economic impact. The aim of the present study was to estimate the prevalence of excretion of EHV-3 in mares without clinical symptoms under field conditions and the re-excretion patterns of the virus in two seropositive (presumably latently infected) mares maintained in isolation for 11 mo. The EHV-3 virus was detected in perineal-vaginal swabs by real time PCR in 14 (6%) of 220 thoro...
Use of a novel serological test for exposure to Streptococcus equi subspecies equi in hospitalised horses.
The Veterinary record    March 9, 2010   Volume 166, Issue 10 294-297 doi: 10.1136/vr.166.10.294
Knowles EJ, Mair TS, Butcher N, Waller AS, Wood JL.Thirty horses with no external signs of strangles were tested for exposure to Streptococcus equi subspecies equi (S equi) using a new, commercially available serological test. The horses were also tested for persistent carriage of S equi by endoscopy of the guttural pouches and PCR analysis of lavage samples. The owners were questioned about the recent medical history of the horses. Serology suggested that four horses had been recently exposed to S equi. None of the horses had a known history of strangles but three of the four seropositive horses had recently shown non-specific signs of respir...
Molecular detection of Theileria equi and Babesia caballi in the bone marrow of asymptomatic horses.
Veterinary parasitology    February 4, 2010   Volume 170, Issue 1-2 182-184 doi: 10.1016/j.vetpar.2010.01.043
Pitel PH, Pronost S, Scrive T, Léon A, Richard E, Fortier G.Equine piroplasmosis is a tick-borne disease, the aetiological agents of which are either Theileria equi or Babesia caballi parasites. Piroplasmosis is commonly encountered in acute or sub-acute clinical forms although clinically recovered horses may remain asymptomatic but infected for several years. The clinical detection of such apparently healthy carrier horses (that serve as a host for subsequent infecting ticks), remains a worldwide challenge for controlling the spread of the disease. The aim of the present paper is to report on the detection of both T. equi and B. caballi by PCR in the ...
Preliminary molecular analysis of Clostridium difficile isolates from healthy horses in northern Italy.
Comparative immunology, microbiology and infectious diseases    December 11, 2009   Volume 33, Issue 6 e25-e29 doi: 10.1016/j.cimid.2009.10.008
Ossiprandi MC, Buttrini M, Bottarelli E, Zerbini L.Clostridium difficile, associated with a wide spectrum of diseases in humans, as well as in several animal species, is an important cause of colitis in adult horses and foals. The aim of this study was to investigate by toxin gene profile and PCR-ribotyping the molecular characteristics of 14 C. difficile strains isolated from 42 faeces of healthy horses. Both toxin genes, tcdA and tcdB, were present in only 1 isolate (7.1%). Six isolates (42.9%) demonstrated tcdA-/tcdB+ genotype, and seven isolates (50.0%) were tcdA-/tcdB-. All strains were binary toxin genes negative (cdtA-/cdtB-). The PCR-p...
Skeletal forelimb measurements and hoof spread in relation to asymmetry in the bilateral forelimb of horses.
Equine veterinary journal    May 28, 2009   Volume 41, Issue 3 238-241 doi: 10.2746/042516409x395561
Wilson GH, McDonald K, O'Connell MJ.Research has highlighted a high frequency of skeletal asymmetries in horses. In addition, research into hoof asymmetries has shown that within a bilateral pair, the hoof with the smaller angle is often subjected to greater loading. There has been limited attention paid to understanding compensatory mechanisms for skeletal asymmetries in the horse; the dynamic structure of the hoof could potentially be acting in a compensatory capacity. Objective: To investigate the relationship between morphometry of forelimb segments and hoof spread and their incidence of asymmetry. Methods: Ten bilateral mea...