Studies on histoplasmosis farciminosi (epizootic lymphangitis) in Egypt. Isolation of Histoplasma farciminosum from cases of histoplasmosis farciminosi in horses and its morphological characteristics

The socioeconomic impact of equine epizootic lymphangitis in working equids in low and middle-income countries: A scoping review

Equine epizootic lymphangitis (EEL) is a very infectious and contagious fungal disease that, with its ocular, respiratory and skin forms, causes severe effects on the health and welfare of working equids. Treatment is expensive and rarely available in low and middle-income countries (LMICs). Epidemiological data is lacking in most countries where the disease is known to exist. The purpose of this scoping review is to identify the current knowledge on the socioeconomic impact of EEL in working equids in LMICs, to highlight knowledge gaps and provide recommendations for future research. Seven eligible papers were obtained from the search of four databases and backward citation searching. The review showed that the available research on this subject is very scarce and restricted to Ethiopia. From the results it emerged that EEL causes detrimental socioeconomic effects on working equids' owners, compromising their health and livelihood. Its economic consequences were attributed to the reduced working capacity and loss of sick animals. Among the social impacts, authors highlighted the stigma around sick equids and their owners. Further studies on the socioeconomic impact of EEL conducted in endemic areas are highly required. The integration of epidemiological data with socioeconomic impact studies from LMICs may promote funding allocation for the development of cost-effective treatments and vaccines and for implementing disease prevention and control programmes. Future research would gain from applying the One Health approach to better examine the multiplicity of the disease socioeconomic effects, therefore increasing the potential of research to orientate policy.

Equine Histoplasmosis in Ethiopia: Phylogenetic Analysis by Sequencing of the Internal Transcribed Spacer Region of rRNA Genes

Equine histoplasmosis commonly known as epizootic lymphangitis (EL) is a neglected granulomatous disease of equine that is endemic to Ethiopia. It is caused by Histoplasma capsulatum variety farciminosum, a dimorphic fungus that is closely related to H. capsulatum variety capsulatum. The objective of this study was to undertake a phylogenetic analysis of H. capsulatum isolated from EL cases of horses in central Ethiopia and evaluate their relationship with H. capsulatum isolates in other countries and/or clades using the internal transcribed spacer (ITS) region of rRNA genes. Clinical and mycological examinations, DNA extraction, polymerase chain reaction (PCR), Sanger sequencing, and phylogenetic analysis were used for undertaking this study. Additionally, sequence data of Histoplasma isolates were retrieved from GenBank and included for a comprehensive phylogenetic analysis. A total of 390 horses were screened for EL and 97 were positive clinically while H. capsulatum was isolated from 60 horses and further confirmed with PCR, of which 54 were sequenced. BLAST analysis of these 54 isolates identified 29 H. capsulatum isolates and 14 isolates from other fungal genera while the remaining 11 samples were deemed insufficient for further downstream analysis. The phylogenetic analysis identified five clades, namely, African, Eurasian, North American 1 and 2, and Latin American A and B. The Ethiopian isolates were closely aggregated with isolates of the Latin American A and Eurasian clades, whereas being distantly related to isolates from North American 1 and 2 clades as well as Latin American B clade. This study highlights the possible origins and transmission routes of Histoplasmosis in Ethiopia.

Epidemiology of epizootic lymphangitis of carthorses in northern Ethiopia using conventional diagnostic methods and nested polymerase chain reaction

BACKGROUND

Epizootic lymphangitis (EL), caused by Histoplasma capsulatum variety farciminosum (HCF) is a contagious, chronic disease of equines, characterized by development of nodular lesions in the lymph nodes, lymphatic vessels and skin. It is one of the most important diseases of equines in Ethiopia, causing significant economic loss, particularly in the livelihood of carthorse owners. To date there is neither effective diagnostic nor control measure implemented in the country. Furthermore, there is a shortage of data on the epidemiology of the disease in different regions of this country. The aim of this study was to investigate epidemiology of EL in northern Ethiopia, using the conventional methods as well as nested polymerase chain reaction (PCR).

RESULTS

The presence of HCF genetic material was confirmed in 44% (84/191) of the carthorses. Subclinical infection was observed in 18.2% (22/121) of the apparently healthy carthorses. Considering the nested PCR as a gold standard, sensitivity and specificity of clinical examination were 74% and 92.5%, respectively, while the area under the ROC curve (AUR) was 0.83 (95% confidence interval, 0.77, 0.896). Moreover, a moderate (k = 0.675) agreement observed between the nested PCR and clinical examination.

CONCLUSIONS

This study demonstrated widespread occurrence of EL in northern Ethiopia, and the advantage of the nested PCR in detecting infection of HCF, even before the clinical symptoms became apparent.

In Vitro Evaluation of the Effects of Selected Plants on the Growth of the Mycelial Form of Histoplasma capsulatum Variety farciminosum in Ethiopia

Epizootic lymphangitis is prevalent in equines in Ethiopia, causing remarkable economic and welfare impacts but often neglected. Lack of effective treatment contributed to its continued occurrence, and hence, search for an effective treatment should be considered a priority area to minimize its impacts. Previous ethnobotanical studies have reported that Curcuma longa, Phytolacca dodecandra, and Datura stramonium were used to treat cutaneous fungal infections and reduce their incidence. The treatment effects of these plants against epizootic lymphangitis should be studied. The in vitro growth inhibitory effects of methanol extracts of the root of C. longa, berry of P. dodecandra, and leaf of D. stramonium were evaluated. Histoplasma capsulatum var farciminosum was isolated from clinical cases of epizootic lymphangitis in carthorses in central Ethiopia. The nested polymerase chain reaction was used to confirm the identity of the isolates. Serial twofold dilutions of the extract of berries of P. dodecandra and leaves of D. stramonium were done in sterile water, whereas dilution of the extract of roots of C. longa was done in dimethylsulphoxide. The effects of the plants on the growth of Histoplasma capsulatum var farciminosum were assessed by agar dilution assay. Culture media with no antifungal agent and media containing ketoconazole served as negative and positive control, respectively. The methanol extract of C. longa showed inhibitory effects at concentrations ranging from 0.07 to 5 mg/mL. Similarly, the methanol extract of P. dodecandra showed growth inhibitory effects at concentrations ranging from 0.156 to 5 mg/mL. That is, the growth inhibitory concentration of C. longa was 0.07 mg/mL, whereas that of P. dodecandra was 0.156 mg/mL. In contrast, D. stramonium showed no inhibitory effect. This preliminary observation showed that methanol extracts of C. longa and P. dodecandra showed inhibitory effects on the growth of Histoplasma capsulatum var farciminosum requiring further repeated in vitro evaluation so as to generate adequate evidence, which would justify in vivo trials.

The global epidemiology of emerging Histoplasma species in recent years

Histoplasmosis is a serious infectious disease in humans caused by Histoplasma spp. (Onygenales), whose natural reservoirs are thought to be soil enriched with bird and bat guano. The true global burden of histoplasmosis is underestimated and frequently the pulmonary manifestations are misdiagnosed as tuberculosis. Molecular data on epidemiology of Histoplasma are still scarce, even though there is increasing recognition of histoplasmosis in recent years in areas distant from the traditional endemic regions in the Americas. We used multi-locus sequence data from protein coding loci (ADP-ribosylation factor, H antigen precursor, and delta-9 fatty acid desaturase), DNA barcoding (ITS1/2+5.8s), AFLP markers and mating type analysis to determine the genetic diversity, population structure and recognise the existence of different phylogenetic species among 436 isolates of Histoplasma obtained globally. Our study describes new phylogenetic species and the molecular characteristics of Histoplasma lineages causing outbreaks with a high number of severe outcomes in Northeast Brazil between 2011 and 2015. Genetic diversity levels provide evidence for recombination, common ancestry and clustering of Brazilian isolates at different geographic scales with the emergence of LAm C, a new genotype assigned to a separate population cluster in Northeast Brazil that exhibited low diversity indicative of isolation. The global survey revealed that the high genetic variability among Brazilian isolates along with the presence of divergent cryptic species and/or genotypes may support the hypothesis of Brazil being the center of dispersion of Histoplasma in South America, possibly with the contribution of migratory hosts such as birds and bats. Outside Brazil, the predominant species depends on the region. We confirm that histoplasmosis has significantly broadened its area of occurrence, an important feature of emerging pathogens. From a practical point of view, our data point to the emergence of histoplasmosis caused by a plethora of genotypes, and will enable epidemiological analysis focused on understanding the processes that lead to histoplasmosis. Further, the description of this diversity opens avenues for comparative genomic studies, which will allow progress toward a consensus taxonomy, improve understanding of the presence of hybrids in natural populations of medically relevant fungi, test reproductive barriers and to explore the significance of this variation.

Worldwide Phylogenetic Distributions and Population Dynamics of the Genus Histoplasma

Background

Histoplasma capsulatum comprises a worldwide complex of saprobiotic fungi mainly found in nitrogen/phosphate (often bird guano) enriched soils. The microconidia of Histoplasma species may be inhaled by mammalian hosts, and is followed by a rapid conversion to yeast that can persist in host tissues causing histoplasmosis, a deep pulmonary/systemic mycosis. Histoplasma capsulatum sensu lato is a complex of at least eight clades geographically distributed as follows: Australia, Netherlands, Eurasia, North American classes 1 and 2 (NAm 1 and NAm 2), Latin American groups A and B (LAm A and LAm B) and Africa. With the exception of the Eurasian cluster, those clades are considered phylogenetic species.

Methodology/Principal Findings

Increased Histoplasma sampling (n = 234) resulted in the revision of the phylogenetic distribution and population structure using 1,563 aligned nucleotides from four protein-coding regions. The LAm B clade appears to be divided into at least two highly supported clades, which are geographically restricted to either Colombia/Argentina or Brazil respectively. Moreover, a complex population genetic structure was identified within LAm A clade supporting multiple monophylogenetic species, which could be driven by rapid host or environmental adaptation (~0.5 MYA). We found two divergent clades, which include Latin American isolates (newly named as LAm A1 and LAm A2), harboring a cryptic cluster in association with bats.

Conclusions/Significance

At least six new phylogenetic species are proposed in the Histoplasma species complex supported by different phylogenetic and population genetics methods, comprising LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1 phylogenetic species. The genetic isolation of Histoplasma could be a result of differential dispersion potential of naturally infected bats and other mammals. In addition, the present study guides isolate selection for future population genomics and genome wide association studies in this important pathogen complex.

Histoplasmosis is a potentially severe fungal disease of mammals caused by Histoplasma capsulatum. The highest incidence of the disease is reported on the American continent, and approximately 30% of HIV and histoplasmosis co-infections are fatal. Previous studies have suggested at least 7 phylogenetic species within H. capsulatum, however by increasing taxon sampling and using different phylogenetic and population genetic methods, we detect at least 5 additional phylogenetic species within Latin America (LAm A1, LAm A2, LAm B1, LAm B2, RJ and BAC-1). These phylogenetic species are nested in the former LAm A clade. We found evidence that bats may be a cause of speciation in Histoplasma, as well-supported monophyletic clades were found in association with different species of bats. The radiation of the Latin American H. capsulatum species took a place around 5 million years ago, which is consistent with the radiation and diversification of bat species. Previous phylogenetic distribution of Histoplasma is upheld and strong support is indicated for the species delineation and evolution of this important pathogen.

Participatory appraisal of the impact of epizootic lymphangitis in Ethiopia

Epizootic lymphangitis (EZL) is reported to have a significant impact upon livelihoods within resource-poor settings. This study used a participatory approach to explore peoples' experiences of EZL and examine the perceived impact of disease, owner knowledge and understanding of EZL, lay management of disease and, attitudes and strategies towards disease prevention. Focus-group discussions were held with 358 cart-horse owners and drivers recruited from 7 towns attended by SPANA (Society for the protection of animals abroad) mobile veterinary clinics and 2 unexposed towns where no SPANA clinics were available. Focus group discussions explored four main research questions: (1) Is EZL recognised by animal owners, and is this considered an important disease in equids? (2) What factors do animal owners associate with the development of disease? (3) What happens to an animal with clinical disease and how does this impact upon the owner/community? (4) Are measures taken to reduce disease occurrence? These key areas were explored using photographs, disease ranking, matrices and open discussion. Data were analysed using descriptive statistics and thematic analysis. The results are presented thematically and include: recognition and descriptions of EZL, treatment strategies used, disease priorities and ranking, impact of disease, disease transmission and attitudes and approaches to disease prevention. EZL was widely recognised and ranked highly as an important disease of equids. However, there was uncertainty around identifying early cases of EZL, and this could impact upon the timing of initiating treatment and separating potentially infectious animals. People had varying knowledge of effective methods for disease prevention and reported particular difficulties with isolating infected animals. The impact of EZL was multi-dimensional and encompassed effects upon the horse, the individual owner and the wider society. Working equids provide a vital utility and source of income to many people in resource-poor settings. Often, infection with EZL resulted in a reduction in working ability which had a direct impact upon the livelihoods of owners and their dependent family members. EZL also impacted upon the welfare of the horse as sick animals continued to be worked and, in advanced cases, horses were abandoned due to ineffective or unavailable treatment. This study conceptualises the importance of EZL due to the effects of the disease on the horse and its impact upon human livelihoods. Epizootic lymphangitis is a neglected disease that requires further investigation in order to develop practical and sustainable disease control strategies within endemic regions.

Histofarcin test for the diagnosis of epizootic lymphangitis in Ethiopia: development, optimisation, and validation in the field

Histofarcin, a skin test antigen for the diagnosis of epizootic lymphangitis, was locally produced from the mycelial form of Histoplasma capsulatum var. farciminosum (HCF) in disease-endemic districts of Ethiopia and tested for its application in the field between April 2002 and May 2003. The test was evaluated using 108 mules, 84 in endemic and 24 in disease-free districts. Microscopic and mycological examinations of clinical lesions were used as the "gold standard" for the validation of the test. The concentration of histofarcin that caused an optimum reaction was 0.2-0.4 mg/mL in a 0.1 mL dose and this was attained 24-48 h post-injection. The sensitivity and specificity of the histofarcin test were 90.3% (CI = 73.1, 97.5) and 69% (95%, CI = 48.1, 84.9%) in disease-endemic districts. On the other hand, specificity was 100% (CI=94.8, 100) in disease-free districts. Positive and negative predictive values of the histofarcin test were 77.78% (95% CI = 60.4, 89.3) and 85.71% (95% CI = 62.6, 96.2), respectively. A marginal substantial agreement (kappa = 0.61, P = 0.0000) was observed between the clinical status and the result of the histofarcin test. A large proportion (31%) of 'false positives' was recorded in endemic districts, which could be due to the pre-clinical stage of the disease. The latter ended in lower specificity and positive predictive value of the test since the true infection status of a 'false positive' could not be known on the basis of clinical features. Therefore, standard test validation procedures including slaughtering and isolation of HCF is required. After proper validation, we conclude that the histofarcin test could play a significant role in detecting early infection, and differentiating of EL from glanders, ulcerative lymphangitis, and sporotrichosis.

Preliminary trial on the reproducibility of epizootic lymphangitis through experimental infection of two horses

Epizootic lymphangitis (EL) was experimentally reproduced in four horses that had been purchased from an EL-free district. Two horses were injected with either 0.2 mL of the yeast form of Histoplasma capsulatum var. farciminosum (HCF) in pus (Horse 1), or 0.2 mL (ca. 20 mg) of a suspension in saline of the mycelial form (Horse 2), both into the pre-scapular and pre-femoral lymph nodes, with scarification of the skin of the left hind limb, conjunctiva of the right eye and the nasal membrane of the right nostril. The two other horses served as controls. Nodular lesions of EL appeared during the fourth week of infection at all sites in the horse infected with the yeast form. Lesions only appeared in the lymph nodes and skin scratches of the horse infected with the mycelial suspension after three months. The control horses showed no clinical signs. The yeast form was recovered from the lesions of both infected horses. Similarly, the mycelial form was isolated from both horses on Sabouraud's Dextrose Agar. This experiment showed the reproducibility of clinical EL through experimental infection, and has laid the groundwork for the evaluation of the potency of a vaccine against EL using a vaccination and challenge experiment.

A cross-sectional study of epizootic lymphangitis in cart-mules in western Ethiopia

A cross-sectional study was conducted to determine the prevalence of epizootic lymphangitis (EL) in 309 cart-mules (cart-pulling mules) in Bako and Ejaji towns, Western Ethiopia using clinical and microbiological examinations, between November 2002 and April 2003. The overall prevalence was 21% (CI=16.6-26%). The clinical, histological and mycological characteristics of EL in a cart-mule were similar with those in a horse. There was significant (chi2=133.5, P=0.001) association between tick infestation and EL lesions in study cart-mules. Amblyoma coherence and Boophilus genera were the ticks collected from lesions of cases of EL, and thus played a predisposing role. In conclusion, our results showed that EL has high prevalence in cart-mules in the two towns.

Keratitis due to Histoplasma spp. in a horse

A 5-year-old Holsteiner gelding from Germany was presented 2 months after a whitish discoloration of the left cornea was observed. Cytologic examination revealed intra- and extracellular globular structures, up to 4 micro m in size, consisting of a central spherical deeply basophilic body surrounded by an unstained halo. The structures were morphologically consistent with Histoplasma spp. Infection with Histoplasma organisms is not endemic in Europe. Topical use of fluconazole was successful in eliminating Histoplasma organisms within 10 days of initiation of treatment.

Molecular taxonomy and epidemiology of Blastomyces and Histoplasma species

Cladistic analysis of partial 26S rRNA sequences was used to estimate evolutionary distances among species and varieties of the dimorphic onygenalean genera Blastomyces, Coccidioides, Emmonsia, Histoplasma and Paracoccidioides. With the exception of Coccidioides, all genera were closely related, with about 5% base differences and even less (1-2%) between Blastomyces and Emmonsia. These data were supported by a teleomorph in the same genus Ajellomyces. In a phylogenic study of a wide range of ascomycete orders and families, Coccidioides immitis was found to be closest to Aphanoascus fulvescens and Chrysosporium keratinophilum, and to have relative distances to the remaining dimorphic genera (family Onygenaceae) similar to those of the dermatophytes (family Arthrodermataceae). The sequencing data were confirmed by genomic comparisons. All dimorphic genera had a nuclear DNA base composition in the same range of 46.6-47.3% G + C. The DNA melting curves of Blastomyces and Histoplasma strains showed irregularities that were ascribed to the presence of AT-rich stretches in satellite DNA rather than in mitochondrial DNA. Derivative profiles proved to be highly reproducible within regional populations and coincided with differences in clinical behaviour of each species. Blastomyces dermatitidis generated two kinds of curves, corresponding to the geographically distinct serotypes 1 and 2. The African type (serotype 2) was characterized by a classical sigmoidal melting curve similar to that for all strains of Coccidioides, Emmonsia and Paracoccidioides. In contrast, the American type (serotype 1) contained satellite DNA (27% G + C). A rRNA base difference of 1.5% was observed between geographical types, a value slightly higher than that noted between Histoplasma capsulatum and its variety farciminosum (0.9%). All three H. capsulatum varieties presented irregularities in their DNA melting curves. The molecular data support the recognition of two of them as agents of blastomycosis and the assignment of more than one species and two varieties to the genus Emmonsia.

Ocular histoplasmosis due to Histoplasma farciminosum in Egyptian donkeys

In this study 19 donkeys suffering from face excoriations below the medial canthas and lesions in the lacrymal apparatus were subjected to clinical radiological and microbiological investigations. Also histopathological examination of biopsy materials from ocular lesions were made. Eleven out of 19 donkeys (57.9%) showed specific lesions in the lacrymal apparatus. Mycological examination revealed the isolation of Histoplasma cells from 10 out of 19 examined cases. The isolated Histoplasma culture, although not completely identical to H. farciminosum, was more related to this than to other Histoplasma species. Histopathological examination revealed the presence of marked tissue infiltration by lymphocytes, monocytes and macrophages. Also the fungal organism appeared as double-contoured yeast cells lying within macrophages and giant cells.