Inapparent Carriers Research Articles

Differences in the genome, methylome, and transcriptome do not differentiate isolates of Streptococcus equi subsp. equi from horses with acute clinical signs from isolates of inapparent carriers.

Streptococcus equi subsp. equi (SEE) is a host-restricted bacterium that causes the common infectious upper respiratory disease known as strangles in horses. Perpetuation of SEE infection appears attributable to inapparent carrier horses because it neither persists long-term in the environment nor infects other host mammals or vectors, and infection results in short-lived immunity. Whether pathogen factors enable SEE to remain in horses without causing clinical signs remains poorly understood. Thus, our objective was to use next-generation sequencing technologies to characterize the genome, methylome, and transcriptome of isolates of SEE from horses with acute clinical strangles and inapparent carrier horses-including isolates recovered from individual horses sampled repeatedly-to assess pathogen-associated changes that might reflect specific adaptions of SEE to the host that contribute to inapparent carriage. The accessory genome elements and methylome of SEE isolates from Sweden and Pennsylvania revealed no significant or consistent differences between acute clinical and inapparent carrier isolates of SEE. RNA sequencing of SEE isolates from Pennsylvania demonstrated no genes that were differentially expressed between acute clinical and inapparent carrier isolates of SEE. The absence of specific, consistent changes in the accessory genomes, methylomes, and transcriptomes of acute clinical and inapparent carrier isolates of SEE indicates that adaptations of SEE to the host are unlikely to explain the carrier state of SEE. Efforts to understand the carrier state of SEE should instead focus on host factors.

Clostridium perfringens type C necrotic enteritis in pigs: diagnosis, pathogenesis, and prevention.

Clostridium perfringens type C causes severe and lethal necrotic enteritis (NE) in newborn piglets. NE is diagnosed through a combination of pathology and bacteriologic investigations. The hallmark lesion of NE is deep, segmental mucosal necrosis with marked hemorrhage of the small intestine. C. perfringens can be isolated from intestinal samples in acute cases but it is more challenging to identify pathogenic strains in subacute-to-chronic cases. Toxinotyping or genotyping is required to differentiate C. perfringens type C from commensal type A strains. Recent research has extended our knowledge about the pathogenesis of the disease, although important aspects remain to be determined. The pathogenesis involves rapid overgrowth of C. perfringens type C in the small intestine, inhibition of beta-toxin (CPB) degradation by trypsin inhibitors in the colostrum of sows, and most likely initial damage to the small intestinal epithelial barrier. CPB itself acts primarily on vascular endothelial cells in the mucosa and can also inhibit platelet function. Prevention of the disease is achieved by immunization of pregnant sows with C. perfringens type C toxoid vaccines, combined with proper sanitation on farms. For the implementation of prevention strategies, it is important to differentiate between disease-free and pathogen-free status of a herd. The latter is more challenging to maintain, given that C. perfringens type C can persist for a long time in the environment and in the intestinal tract of adult animals and thus can be distributed via clinically and bacteriologically inapparent carrier animals.

Rapid detection of salmonellosis due to Salmonella enterica serovar Typhimurium in Peruvian commercially bred cavies, using indigenous wild bacteriophages.

The salmonelloses are among the commonest, most widespread human zoonotic infections. They have generated international networks to attempt their control, since they cause a spectrum of ailments, ranging from inapparent carrier states to full-blown, severe, sometimes deadly diarrheal and systemic disease. Rapid diagnosis is needed for a number of reasons. The aim of this study was to standardize and validate a phage amplification test for the identification of salmonellosis to be applied to infections of Cavia porcellus. Native bacteriophages were isolated from infected cavies and environmental residues from commercial cavy-breeding facilities. Salmonella enterica serovar Typhimurium ATCC 14028 was used to detect, isolate and propagate the bacteriophages, and to standardize a phage amplification assay to detect S. Typhimurium from rectal swabs of cavies. The phage amplification assay was tested using 2 antiviral agents, MgSO4·7H2O (MAS) and pomegranate rind extract (PRE) plus ferrous sulfate (PRE-FeSO4). The final assay format chosen used PRE-FeSO4 and allowed detection of S. Typhimurium in 90 min from culture, 5 h from clinical samples, with a limit of detection at 103 pfu; sensitivity was 98.2%, specificity 98%, negative predictive value (NPV) 96.1%, and positive predictive value (PPV) 99.1%. Bacteriophage amplification is therefore an appropriate, fast procedure for detection of this pathogen in clinical samples.

Rapid detection of equine infectious anaemia virus nucleic acid by insulated isothermal RT-PCR assay to aid diagnosis under field conditions.

Control of equine infectious anaemia (EIA) currently depends on serological diagnosis of infected equids. However, recently infected equids may not produce detectable anti-EIAV antibodies up to 157 days post infection and so present a high transmission risk. Therefore, direct nucleic acid detection methods are urgently needed to improve EIAV surveillance and management programs in counties where the disease is endemic. To evaluate a field-deployable, reverse transcription-insulated isothermal PCR (RT-iiPCR) assay targeting the conserved 5' untranslated region (5' UTR)/exon 1 of the tat gene of EIAV. The analytical and clinical performance of the newly developed EIAV RT-iiPCR was evaluated by comparison with a EIAV real-time RT-PCR (RT-qPCR) along with the AGID test. Analytical sensitivity was determined using in vitro transcribed RNA containing the target area of the 5' UTR/tat gene and samples from two EIAV-positive horses. Specificity was verified using nine common equine viruses. Clinical performance was evaluated by comparison with EIAV RT-qPCR and AGID using samples derived from 196 inapparent EIAV carrier horses. EIAV RT-iiPCR did not react with other commonly encountered equine viruses and had equivalent sensitivity (95% detection limit of eight genome equivalents), with a concordance of 95.41% to conventional EIAV RT-qPCR. However, the RT-qPCR and RT-iiPCR had sensitivities of 43.75 and 50.00%, respectively, when compared to the AGID test. Low viral loads commonly encountered in inapparent EIAV carriers may limit the diagnostic sensitivity of RT-PCR-based tests. Although EIAV RT-iiPCR is not sufficiently sensitive to replace the current AGID test, it can augment control efforts by identifying recently exposed or "serologically silent" equids, particularly as the latter often represent a significant transmission risk because of high viral loads. Furthermore, the relatively low cost and field-deployable design enable utilisation of EIAV RT-iiPCR even in remote regions.

Prevalence of CMV infection among staff in a metropolitan children's hospital - occupational health screening findings.

Background: Staff in children’s hospitals may run an increased risk of cytomegalovirus (CMV) contact infection leading to a congenital CMV fetopathy during pregnancy. The main risk factor is close contact with inapparent carriers of CMV among infants (<3 years). We therefore examined CMV seroprevalence (SP) and possible risk factors for CMV infection among staff at a children’s hospital.Method: In 2014, staff at a metropolitan children’s hospital were offered a CMV antibody test in the context of occupational health screening. Besides of anti-CMV immunoglobulin G (anti-CMV IgG) gender, age, profession, number of children and migration background were assessed and used as independent variables in multiple logistic regression. Women without a migration background (MIG) were considered as a separate group.Results: The study included 219 employees. Women showed a significant higher risk than men of being CMV-positive (adjusted odds ratio [aOR] 3.0; 95% CI 1.1–7.8). The risk among age groups of 30 and over was double that of the under-30s (aOR 2.0; 95% CI 1.0–3.9); among those aged 40-plus it was aOR 2.3 (95% CI 1.1–4.7). Staff with an MIG tested more often positive than those without an MIG (95.5% versus 45.7%). CMV SP was 47.7% among women without an MIG. In this subgroup the probability of CMV infection increased with age (p=0.08) as well. Conclusion: In the staff group as a whole there was a significant correlation between CMV SP, country of origin and age. We found no significant differences between occupational groups; perhaps our random sample was too small. Given the low CMV SP particularly in those without MIG, women who want to have children in particular must be protected from CMV infection. Follow-up studies should be undertaken to test whether good workplace hygiene offers sufficient protection for pregnant women and could be an alternative to prohibiting certain activities.

In situ hybridization and sequence analysis reveal an association of Plasmodium spp. with mortalities in wild passerine birds in Austria.

Native European passerine birds are frequently clinically inapparent carriers of haemosporidian parasites of the genus Plasmodium. Clinical disease and death are only exceptionally reported. In the present study, tissue samples of 233 wild passerine birds found dead in Eastern Austria were examined by in situ hybridization (ISH) and partial cytochrome B gene sequence analysis for the presence, abundance and taxonomic assignment of Plasmodium spp. In 34 cases (14.6%), ISH yielded a positive result with large numbers of developmental stages in different cell types of the spleen, liver, brain and lung. The abundance of the tissue stages, which was comparable to fatal cases of avian malaria in penguins, suggested a major contribution to the cause of death. Genetic analysis revealed infections with representatives of three different valid species of Plasmodium, Plasmodium elongatum, Plasmodium lutzi and Plasmodium vaughani. Genetically identical parasite lineages had been found in a previous study in penguins kept in the Vienna zoo, providing evidence for the role of wild birds as reservoir hosts. Further, this study provides evidence that several species of Plasmodium are able to abundantly proliferate in endemic wild birds ultimately resulting in mortalities.

Differences of immune Env-specific responses between newly EIAV infected and inapparent carrier horses

Differences of immune Env-specific responses between newly EIAV infected and inapparent carrier horses

Epitope shifting of gp90-specific cellular immune responses in EIAV-infected ponies

Unlike other lentiviruses, EIAV replication can be controlled in most infected horses leading to an inapparent carrier state free of overt clinical signs which lasts for many years. While the resolution of the initial infection is correlated with the appearance of virus specific cellular immune responses, the precise immune mechanisms responsible for control of the infection are not yet identified. Since the virus undergoes rapid mutation following infection, the immune response must also adapt to meet this challenge. We hypothesize that this adaptation involves peptide-specific recognition shifting from immunodominant variable determinants to conserved immunorecessive determinants following EIAV infection. Forty-four peptides, spanning the entire surface unit protein (gp90) of EIAV, were used to monitor peptide-specific T cell responses in vivo over a six-month period following infection. Peptides were injected intradermally and punch biopsies were collected for real-time PCR analysis to monitor the cellular peptide-specific immune responses in vivo. Similar to the CMI response to HIV infection, peptide-specific T cell recognition patterns changed over time. Early post infection (1 month), immune responses were directed to the peptides in the carboxyl-terminus variable region. By six months post infection, the peptide recognition spanned the entire gp90 sequence. These results indicate that peptide recognition broadens during EIAV infection.

Development, evaluation, and laboratory validation of immunoassays for the diagnosis of equine infectious anemia (EIA) using recombinant protein produced from a synthetic p26 gene of EIA virus

Equine infectious anemia (EIA)-a retroviral disease caused by equine infectious anemia virus (EIAV)-is a chronic, debilitating disease of horses, mules, and donkeys. EIAV infection has been reported worldwide and is recognized as pathogen of significant economic importance to the horse industry. This disease falls under regulatory control program in many countries including India. Control of EIA is based on identification of inapparent carriers by detection of antibodies to EIAV in serologic tests and "Stamping Out" policy. The current internationally accepted test for diagnosis of EIA is the agar gel immune-diffusion test (AGID), which detects antibodies to the major gag gene (p26) product. The objective of this study was to develop recombinant p26 based in-house immunoassays [enzyme linked immunosorbent assays (ELISA), and AGID] for EIA diagnosis. The synthetic p26 gene of EIAV was expressed in Escherichia coli and diagnostic potential of recombinant p26 protein were evaluated in ELISA and AGID on 7,150 and 1,200 equine serum samples, respectively, and compared with commercial standard AGID kit. The relative sensitivity and specificity of the newly developed ELISA were 100 and 98.6%, respectively. Whereas, relative sensitivity and specificity of the newly developed AGID were in complete agreement in respect to commercial AGID kit. Here, we have reported the validation of an ELISA and AGID on large number of equine serum samples using recombinant p26 protein produced from synthetic gene which does not require handling of pathogenic EIAV. Since the indigenously developed reagents would be economical than commercial diagnostic kit, the rp26 based-immunoassays could be adopted for the sero-diagnosis and control of EIA in India.

Sero-surveillance of equine infectious anemia virus in equines in India during more than a decade (1999–2012)

Equine infectious anemia (EIA) is a retroviral infection of horses. Horses infected by EIA virus (EIAV) become inapparent carriers that remain asymptomatic for the remainder of their life span and serve as infection source to other horses. In this study, agar gel immunodiffusion test and ELISA were used to investigate the presence of antibodies to EIAV in equines. A total of 67,042 equine serum samples from 19 states and two union territories were tested during April 1999 to September 2012. The results revealed that none of the animals were positive for antibodies to EIAV from 1999 to December 2009. However, two EIAV sero-positive cases one each from indigenous and thoroughbred equines were detected in 2010 and 2012, respectively. Occurrence of EIA after a long gap of 11years is indicative of reemergence of EIA in India which warrants concerted efforts in nationwide surveillance and monitoring for detection and elimination of EIAV carrier animals to prevent EIA outbreak.

Genomic and Immunologic analysis of the Chinese attenuated EIAV vaccine

the infection period. Since the virus undergoes rapid mutation following infection, the adaptive immune response must also evolve to meet this challenge. In order to fully understand the evolution of the T cell response during infection, we synthesized forty-four peptides, spanning the entire surface unit protein (gp90) of EIAV, and monitored the peptide-specific T cells responses both in vivo and in vitro over a six month period following challenge. One inapparent carrier (D64) and four recent EIAV infected ponies were included in this study. Peripheral blood mononuclear cells (PBMC) were isolated and stimulated separately with all 44 peptides. The EIAV gp90 epitopes-specific immune responses in vitro were determined by ELISPOT-IFNg assay. In parallel, all peptides were injected intradermally and punch biopsies were collected for real-time PCR tomonitor the cellular immune responses in vivo. As shown by both in vivo and in vitro assays, two of the four recently infected ponies recognized gp90 peptides three weeks post challenge. Similar to the CMI response to HIV infection, peptide-specific T cell recognition patterns changed over time. While some peptides were recognized throughout the sampling period, other peptides were only recognized at the later time points. Also, the response to some specific peptides disappeared after 6 months post infection. By contrast, peptide recognition by the inapparent carrier (D64) was more stable. The mechanisms responsible for this change remain unclear, but this dynamic shift in the immunodominant epitopes hierarchy in the newly infected horses may be the result of mutations in specific epitopes leading to an escape from T cell recognition. In the inapparent carrier, persistent recognition focusing on the more conserved peptides results in a more effective T cell response where virus replication is tightly controlled. These results indicate that T cell responses evolve during the early stage of EIAV infection. This interaction between virus mutation and T cell evolution needs to be considered when designing vaccines.

The determination of in vivo envelope-specific cell-mediated immune responses in equine infectious anemia virus-infected ponies

Distinct from human lentivirus infection, equine infectious anemia virus (EIAV)-infected horses will eventually enter an inapparent carrier state in which virus replication is apparently controlled by adaptive immune responses. Although recrudescence of disease can occur after immune suppression, the actual immune correlate associated with protection has yet to be determined. Therefore, EIAV provides a model for investigating immune-mediated protective mechanisms against lentivirus infection. Here, we have developed a method to monitor EIAV-envelope specific cellular immunity in vivo. An EIA carrier horse with no clinical signs infected 7 years ago and 4 related experimental ponies infected 6 months previously were used in this study. Forty-four 20-mer peptides, representing the entire surface unit protein (gp90) of EIAV, were combined into 14 peptide pools and intradermally injected into the neck of EIAV-infected horses. An identical volume of saline alone was injected into a fifteenth site as a negative control. After 48h, those sites with palpable infiltrations were measured prior to the collection of 2mm and 4mm punch biopsies. Total RNA was extracted from each 2mm biopsy for determination of CD3 and interferon-γ (IFN-γ) mRNA expression by real-time PCR. The 4mm skin biopsies were formalin-fixed and paraffin-embedded for immunohistochemistry (IHC) staining for CD3, CD20, CD25 and MAC387 (macrophage marker). Peripheral blood mononuclear cells (PBMC) were obtained prior to the injection and tested for in vitro reactivity against the same peptides. Histological examination showed that some of the envelope peptides elicited a lymphocytic cellular infiltration at the injection site, as evidenced by positive staining for CD3. Gp90 peptide-specific increases in CD3 and IFN-γ gene expression were also detected in the injection sites. Furthermore, differences were found between in vivo and in vitro responses to gp90 specific peptides. These results demonstrate a novel method for detecting in vivo cell-mediated immune responses to EIAV-specific peptides that is readily applicable to other host/pathogen systems.

Detection, molecular characterization and phylogenetic analysis of full-length equine infectious anemia (EIAV) gag genes isolated from Shackleford Banks wild horses

The genetically distinct wild horse herds inhabiting Shackleford Banks, North Carolina are probably the direct descendents of Spanish stock abandoned after failed attempts to settle mid-Atlantic coastal regions of North America in the Sixteenth Century. In a 1996 island survey, 41% of the gathered horses were discovered seropositive for Equine Infectious Anemia Virus (EIAV) with additional cases identified in 1997 and 1998. As a result of their unique genetic heritage, EIAV seropositive individuals identified in the two latter surveys were transferred to a quarantine facility on the mainland. In September 2008 two of the horses SB1 and SB2 after 10 and 11 years in quarantine respectively, developed clinical signs of EIA. In the case of SB2 these were so severe that the only humane option was euthanasia. Although SB1, survived it experienced a second clinical episode one month later. In May 2009, a third horse in quarantine, SB3, developed extremely severe clinical EIA and was euthanized. This demonstrates naturally infected long-term inapparent carriers can experience recrudescence of very severe disease many years after initial exposure to EIAV. Phylogenetic analysis of complete EIAV gag gene sequences obtained from each of three Shackleford horses demonstrated they were infected with very closely related viruses. Although these were distinguishable from all other strains examined, they belong to a monophyletic group comprising almost exclusively of New World isolates that is distinct from a number of recently characterized Central European EIAV strains.

Recombinant envelope protein (rgp90) ELISA for equine infectious anemia virus provides comparable results to the agar gel immunodiffusion

Equine infectious anemia (EIA) is an important viral infection affecting horses worldwide. The course of infection is accompanied generally by three characteristic stages: acute, chronic and inapparent. There is no effective EIA vaccine or treatment, and the control of the disease is based currently on identification of EIAV inapparent carriers by laboratory tests. Recombinant envelope protein (rgp90) was expressed in Escherichia coli and evaluated via enzyme-linked immunosorbent assay (ELISA). There was an excellent agreement (95.42%) between the ELISA results using rgp90 and agar gel immunodiffusion test results. AGID is considered the "gold-standard" serologic test for equine infectious anemia (EIA). After 1160 serum samples were tested, the relative sensitivity and specificity of the ELISA were 96.1% and 96.4%, respectively. Moreover, analysis diagnostic accuracy of the ELISA was performed. The ELISA proved robust. Furthermore, good reproducibility was observed for the negative controls and, positive controls for all plates tested.

Anemia infecciosa equina

A Anemia Infecciosa Equina (AIE) é uma doença viral crônica, causada por um vírus da família Retroviridae, gênero Lentivirus, limitada a equinos, asininos e muares, caracterizada por episódios periódicos de febre, anemia hemolítica, icterícia, depressão, edema e perda de peso. A AIE gera embargos ao trânsito de equídeos, além de interferir nos eventos esportivos equestres, assumindo assim uma relevância econômica considerável. O agente é transmitido primariamente por picadas de tabanídeos (Tabanus sp.) e moscas dos estábulos (Stomoxys calcitrans) sendo estes apenas vetores mecânicos. Os principais reservatórios da enfermidade são os portadores inaparentes do vírus, principalmente em tropas que não sofrem monitoramento sorológico periódico. A transmissão é mais comum nas épocas mais quentes do ano e em regiões úmidas e pantanosas. A prova da imunodifusão em gel de Agar (IDGA) é considerada o teste padrão-ouro. No Brasil, os laboratórios e técnicos interessados em realizar o diagnóstico devem ser cadastrados no Ministério da Agricultura. As medidas de controle para limitar a disseminação do vírus se baseiam principalmente em testes sorológicos de rotina e na remoção dos animais reagentes do plantel, além da restrição ao deslocamento de animais, do teste dos novos animais a serem introduzidos nas tropas, do controle da população de vetores e do não compartilhamento de seringas, agulhas e outros utensílios que possam ser veículo de células infectadas. No Brasil, os animais positivos no teste de IDGA devem ser sacrificados, conforme estabelecido pelo Programa Nacional de Sanidade dos Equídeos do Ministério da Agricultura. O estudo dos aspectos biológicos, epidemiológicos e profiláticos da doença se apresenta fundamental para o controle desta enfermidade e, consequentemente para o sucesso da equinocultura de qualquer país ou região onde a mesma se faz presente.

First report on seroepidemiological and clinical investigation of cat infection with Bartonella henselae in the area of Novi Sad, Serbia

Cat Scratch Disease (CSD) is an infective disease of animals and humans caused with Bartonella henselae. Prevalence of infection varies between 0 and 68% depending on different population of cats and geographical region. Naturally infected cats are often clinically healthy and are inapparent germ carriers. In this investigation 40 cats from the area of Novi Sad were analyzed. After the epidemiological questionnaire was made, all cats were clinically investigated. To determine the presence of specific antibodies of class G on Bartonella henselae the method of indirect immunofluorescence was used. For the first time in Serbia, in the area of Novi Sad municipality the infection caused by Bartonella henselae in the population of cats was detected. Prevalence of specific antibodies of class IgG on Bartonella henselae antigen in the population of cats was 57%. The most common clinical manifestations in seropositive cats were gingivitis and lymphoadenopathy.

Recovery of Mycoplasma agalactiae from the ears of goats experimentally infected by the intramammary route

The role of inapparent carriers of Mycoplasma agalactiae and the strategies used to colonise the external ear canal in goats remain unclear. This study examined the ability of M. agalactiae to colonise the ears of goats infected experimentally by the intramammary route. The right mammary glands of 15 lactating goats were inoculated with 10(10) colony forming units (cfu) of M. agalactiae. The goats were randomly assigned to three groups of five animals each and sampled at slaughter at 5, 15 or 45 days post-infection (dpi). A further four goats served as uninfected controls. Right and left ear swabs were collected for detection of M. agalactiae by culture before and after sacrifice. M. agalactiae was detected in 19/20 (95%) ear swabs from goats sampled at 15 and 45dpi, whereas all ear swabs collected before inoculation, ear swabs collected from the group sampled at 5dpi and ear swabs from control goats at the time of sacrifice were negative for M. agalactiae. Blood samples collected at 6, 12, 24, 48 and 72h post-infection for detection of M. agalactiae by culture were also negative. There were differences in the antigenic profiles of isolates recovered from the ears compared to the 7MAG strain used to inoculate the animals and most isolates from the mammary gland, milk and supramammary lymph nodes.

In vivo evolution of the gp90 gene and consistently low plasma viral load during transient immune suppression demonstrate the safety of an attenuated equine infectious anemia virus (EIAV) vaccine

To study the in vivo evolution of the attenuated Chinese equine infectious anemia virus (EIAV) vaccine, viral gp90 gene variation and virus replication in immunosuppressed hosts were investigated. The results showed that after vaccination, the gp90 gene followed an evolutionary trend of declining diversity. The trend coincided with the maturation of immunity to EIAV, and eventually, the gp90 gene became highly homologous. The sequences of these predominant quasispecies were consistently detected up to 18 months after vaccination. Furthermore, after transient immune suppression with dexamethasone, the plasma viral RNA copy number of the vaccine strain in three vaccinated ponies remained consistently below the "pathogenic threshold" level, while the viral load increased by 25,000-fold in the positive control of an inapparent carrier of the parental virulent strain. This study is the first to provide evidence for the safety of an attenuated lentiviral vaccine with decreased genomic diversity and consistently low viral replication under suppressed immunity.

Equine Infektiöse Anämie (EIA)

Equine Infectious Anemia (EIA) is a reportable, eradicable epizootic disease caused by the equine lentivirus of the retrovirus family which affects equids only and occurs worldwide. The virus is transmitted by blood, mainly by sanguivorous insects. The main symptoms of the disease are pyrexia, apathy, loss of body condition and weight, anemia, edema and petechia. However, infected horses can also be inapparent carriers without any overt signs. The disease is diagnosed by serological tests like the Coggins test and ELISA tests. Presently, Switzerland is offi cially free from EIA. However, Switzerland is permanently at risk of introducing the virus as cases of EIA have recently been reported in different European countries.

ATTEMPTED TREATMENT OF TIGERS (PANTHERA TIGRIS) INFECTED WITH MICROSPORUM CANIS

An outbreak of dermatophytosis caused by Microsporum canis occurred in tigers (Panthera tigris) at an exotic felid sanctuary in 2003. In an attempt to find an effective, practical, safe, and affordable method for controlling this epizootic, a clinical treatment trial was conducted. Nonalopecic tigers were studied to address the inapparent carrier state observed at the facility. The efficacy of three topical and environmental treatment combinations of a 2% lime sulfur solution and a peroxide-based cleaner were evaluated in nonalopecic, culture-positive tigers (n = 18) housed in four separate enclosures. Lime sulfur solution was applied topically to all of these animals. As a control, nonalopecic but culture-positive tigers (n = 6) housed in two other enclosures were not treated. Environmental treatments included lime sulfur solution (n = 1), a peroxide-based cleaner (n = 1), and no treatment (n = 2). All solutions were applied at 2-wk intervals for seven treatments. The 2% lime sulfur solution treatments were unsuccessful in resolving infections in most tigers. Lime sulfur was effective in suppressing environmental fungal growth immediately posttreatment, whereas the peroxide-based cleaner was not effective. A follow-up survey of all study tigers and their enclosures was conducted 2 yr later, at which time 22 of 24 tigers (92%) had attained resolution, defined as two sequential negative hair cultures. Review of the culture results during the clinical trial and follow-up study suggests that nonalopecic dermatophytosis in tigers that are housed outdoors may not warrant aggressive individual or environmental treatment, as the infection may clear with time.