Cutaneous pythiosis in horses from Brazil

Equidae pythiosis in Brazil and the world: a systematic review of the last 63 years (1960-2023)

This systematic review compiles reports of clinical pythiosis in horses, mules and donkeys from 1960 to 2023 worldwide, focusing on Brazil. We searched databases and included 71 articles detailing clinical characteristics, geographic distribution, epidemiology, diagnostic methods, therapies, and outcomes. The results showed that publications on equine pythiosis have significantly increased since 2010. Brazil reported the highest incidence, comprising 55% of cases, predominantly in the southern, northeastern, and central-western regions during summer and autumn. Cutaneous pythiosis was the most prevalent form, generally presenting as single lesions in the appendicular region, and affected females more than males. Diagnosis typically involved histopathology, used alone or with other methods. Various treatments have been employed, with surgery, often combined with chemotherapy and immunotherapy, being the most common. Notably, 80.84% of treated animals recovered, highlighting the effectiveness of these therapies in enhancing survival rates. The limitations of the study included the lack of data in published case reports, which made it difficult to collect and calculate epidemiological data. Additionally, we recognize that pythiosis in Brazil is underreported, since this disease does not have mandatory notification and several cases are not registered and/or reported in the literature. Lastly, it is hypothesized that equid pythiosis may be more widespread than currently known, and its real occurrence in Brazil remains uncertain.

History and Perspective of Immunotherapy for Pythiosis

The fungus-like microorganism Pythium insidiosum causes pythiosis, a life-threatening infectious disease increasingly reported worldwide. Antimicrobial drugs are ineffective. Radical surgery is an essential treatment. Pythiosis can resume post-surgically. Immunotherapy using P. insidiosum antigens (PIA) has emerged as an alternative treatment. This review aims at providing up-to-date information of the immunotherapeutic PIA, with the focus on its history, preparation, clinical application, outcome, mechanism, and recent advances, in order to promote the proper use and future development of this treatment modality. P. insidiosum crude extract is the primary source of immunotherapeutic antigens. Based on 967 documented human and animal (mainly horses) pythiosis cases, PIA immunotherapy reduced disease morbidity and mortality. Concerning clinical outcomes, 19.4% of PIA-immunized human patients succumbed to vascular pythiosis instead of 41.0% in unimmunized cases. PIA immunotherapy may not provide an advantage in a local P. insidiosum infection of the eye. Both PIA-immunized and unimmunized horses with pythiosis showed a similar survival rate of ~70%; however, demands for surgical intervention were much lesser in the immunized cases (22.8% vs. 75.2%). The proposed PIA action involves switching the non-protective T-helper-2 to protective T-helper-1 mediated immunity. By exploring the available P. insidiosum genome data, synthetic peptides, recombinant proteins, and nucleic acids are potential sources of the immunotherapeutic antigens worth investigating. The PIA therapeutic property needs improvement for a better prognosis of pythiosis patients.

An initial survey of 150 horses from Thailand for anti-Pythium insidiosum antibodies

INTRODUCTION

Pythium insidiosum causes a life-threatening infection termed pythiosis in humans and other animals. The organism has been identified in tropical and subtropical environments worldwide. Since 1985, human pythiosis has been increasingly reported from Thailand. Seroprevalence studies estimated that 32,000 Thai people had been exposed to the pathogen. In 2018, the first animal pythiosis case in Thailand was diagnosed in a horse. Here, we investigated the seroprevalence of anti-P. insidiosum antibodies in the Thai equine population.

MATERIALS AND METHODS

We surveyed serum anti-P. insidiosum antibodies in 150 horses distributed across Thailand, using three established serological tests: enzyme-linked immunosorbent assay (ELISA), immunochromatographic test (ICT), and Western blot analysis.

RESULTS

ELISA detected the anti-P. insidiosum antibodies in three horses. ICT and Western blot confirmed the presence of the antibodies in one of the ELISA-positive horses. Based on one positive out of 150 horses tested, the seroprevalence of anti-P. insidiosum antibodies in the Thai equine population was 0.7%, which is markedly higher than that in the Thai human population (0.07%), but much lower than that in the Brazilian equine population (11.1%).

CONCLUSION

The seroprevalence of the anti-P. insidiosum antibodies in the equine population suggests a higher incidence of pythiosis in horses than in humans. The antibody surveillance reported by our group was undertaken to promote a better understanding of the epidemiology and host susceptibility of pythiosis in Thailand.

GASTRIC PYTHIOSIS IN A BACTRIAN CAMEL ( BACTRIANUS CAMELUS)

Pythium insidiosum, an aquatic oomycete, causes chronic lesions in the skin and digestive tract of multiple species. A captive-bred Bactrian camel ( Camelus bactrianus) showed clinical signs of lethargy and weight loss in a clinical course of 30 days, with no response to treatment. At necropsy, the abdominal cavity had approximately 32 L of a yellow, turbid fluid with fibrin. The third compartment of the stomach (C-3) showed a focal area of rupture covered with fibrin. Close to this area, the C-3 wall was thickened and firm, demonstrating irregular, yellow, and friable areas on cut surface (kunkers). Microscopically, these corresponded to necrosis, characterized by a central amorphous eosinophilic material, surrounded by a pyogranulomatous inflammatory infiltrate and fibrosis. Negatively stained hyphae were observed at the periphery of the necrotic areas, which showed marked immunostaining for P. insidiosum. Pythiosis in camelids may involve the stomach, resulting in peritonitis and death.

Influence of temperature on in vitro zoosporogenesis of Pythium insidiosum

This study verified the influence of different temperatures on P. insidiosum in vitro zoosporogenesis. P. insidiosum isolates (n = 26) were submitted to zoosporogenesis and incubated at 5°C, 15°C, 20°C and 37°C (1st stage). Grass fragments were evaluated under optical microscopy at 4, 8, and 24 hours of incubation. Afterward, all isolates were incubated at 37°C and assessed at the same periods of time (2nd stage). The development of hyphae, presence of vesicles, zoosporangia and zoospores were checked. Only the presence of short hyphae was observed at 5°C. At 15°C, the hyphae were either under development or elongated and two isolates produced zoospores. When the isolates were submitted to 20°C for 4 hours, the presence of long and mycelial hyphae, vesicles, zoosporangia and zoospores was observed, which also happened at the other periods evaluated. In the second stage, the isolates which were initially at 5°C and 15°C evidenced long developing hyphae with the presence of vesicles, zoosporangia, and zoospores within 4 hours of incubation, and these characteristics were kept at the other evaluated periods. The isolates kept at 37°C showed evident zoosporogenesis in the first 4 hours of evaluation. It was concluded that temperatures of 20°C and 37°C support P. insidiosum zoosporogenesis process. On the other hand, 5°C and 15°C temperatures do not kill the microorganism.

Outbreaks of Pythiosis in Two Flocks of Sheep in Northeastern Brazil

Two outbreaks of cutaneous pythiosis caused by Pythium insidiosum were diagnosed in two herds of crossbred hair wool sheep of different ages in the semiarid region of Northeastern Brazil. In one herd of 120 sheep, 40 were affected. The other outbreak affected six sheep out of 80. Local swellings with ulcerative lesions were observed in the limbs and abdominal and prescapular regions. Three sheep were necropsied. Two of them had lung metastasis characterized by multifocal nodules measuring 0.5–2 cm. In one animal, the prescapular lymph node was also affected. In another, the cutaneous lesion extended to the sesamoid bone. Microscopically, there were multifocal granulomas with intralesional P. insidiosum hyphae and Splendore-Hoeppli material surrounding the hyphae. The diagnosis was based on the histologic lesions, immunohisto-chemical identification, and culture of the etiologic agent. One sheep treated with potassium iodide recovered. Standing in swampy water for long periods in a warm aquatic environment seems to be the reason for the high prevalence of the disease.

Evaluation of intravenous regional perfusion with amphotericin B and dimethylsulfoxide to treat horses for pythiosis of a limb

BACKGROUND

Treatment for horses with pythiosis of a limb is challenging. This study aims to evaluate the effects of administering amphotericin B in a 10 % solution of dimethylsulfoxide by intravenous regional limb perfusion (IRLP) to treat horses for cutaneous pythiosis of a limb.

RESULTS

All 15 of the horses treated had complete resolutions of their lesion between 6 to 9 weeks after a single IRLP treatment. No complications were observed at the site of venipuncture for IRLP. Before initiation of treatment, there was anemia and marked leucocytosis which resolved following treatment. Serum biochemistry showed no significant changes.

CONCLUSIONS

IRLP administration of amphotericin B in a 10 % DMSO solution was easily performed, relatively inexpensive and an effective treatment for treating horses for pythiosis of a limb and resolved the infection with no complications.

Utilização da técnica de imuno-histoquímica para confirmar casos de pitiose cutânea equina diagnosticados por meio de caracterização clínica e avaliação histopatológica

Avaliaram-se 12 feridas granulomatosas em membros torácicos e pélvicos de equinos da raça Pantaneira. Foi realizado diagnóstico sugestivo para pitiose cutânea de acordo com as características clínicas das feridas e avaliação histopatológica, com as colorações de hematoxilina-eosina (HE) e Prata Metenamina de Grocott (GMS). A confirmação do diagnóstico foi realizada por exame imuno-histoquímico, método streptavidina-biotina marcada (LSAB). O diagnóstico histopatológico foi de dermatite piogranulomatosa, focal extensa, acentuada, associada a "pseudo-hifas" características de Pythium insidiosum (pitiose cutânea), nos 12 animais desta pesquisa. O diagnóstico de pitiose foi confirmado em 100% dos casos pela imunomarcação positiva (LSAB) para Pythium insidiosum, caracterizada pela visualização de estruturas ramificadas e septadas, sendo observados 100% de paridade entre as técnicas. É possível concluir que a caracterização clínica das feridas granulomatosas com aspecto de pitiose em equinos associada ao resultado histopatológico sugestivo para pitiose equina constituem métodos de diagnóstico confiáveis, os quais podem ser confirmados pela técnica de imuno-histoquímica.

Pitiose cutânea em bovinos na região Sul do Rio Grande do Sul

Descreve-se a ocorrência de pitiose cutânea em bovinos de corte na região sul do Rio Grande do Sul. Os animais foram introduzidos em área alagada e desenvolveram lesões cutâneas ulcerativas e úmidas, de tamanhos variados, localizadas na região distal dos membros e no chanfro nasal. Histologicamente, as lesões eram caracterizadas por múltiplos granulomas com hifas intralesionais, melhor observadas pela coloração de metenamina nitrato de prata de Gomori, e circundadas por abundante tecido conjuntivo fibroso. O diagnóstico foi realizado com base na epidemiologia, lesões macroscópicas e histológicas e pela reação imuno-histoquímica positiva com anticorpo policlonal anti-Pythium insidiosum. A morbidade foi de 23,8% e os animais adoeceram 15-90 dias após a introdução na área alagada. Em todos os casos as lesões evoluíram para a cura sem tratamento. Sugere-se que a doença possa ser mais frequente em bovinos do que se supõe, principalmente em áreas alagadas da região Sul do Rio Grande do Sul.

Three types of immunotherapics against pythiosis insidiosi developed and evaluated

Pythiosis is a granulomatous disease of horses, cattle, dogs, cats and humans identified in tropical and subtropical areas and caused by Pythium insidiosum, a zoosporic fungus. Experimental models of pythiosis in naturally infected species have not yet been reported but, rabbits may be inoculated with zoospores as an experimental model for studying the disease. The present study evaluates the efficacy of three different of immunotherapics in the rabbit model. Approximately 17500 zoospores of oomycete P. insidiosum (CBS 101555 strain) were inoculated in each animal to generate the disease. Immunotherapics were produced from vortexed or sonicated cultures of the same strain. Four groups of five animals were employed: group 1, placebo; group 2, sonicated immunotherapic; group 3, mixed immunotherapic; and group 4, vortexed immunotherapic. All rabbits were inoculated with viable zoospores one month before administration of the immunotherapics. Eight doses of immunotherapic or placebo were used in each animal with a 14 day interval between injections. Rabbits receiving the vortexed immunotherapic were most effectively protected (P<0.05), showing a decrease in the area of coastal nodules due to Pythiosis insidiosum by 71.8% after 26 weeks of evaluation. Moreover, two animals in this group showed complete remission of the infection at the end of the 26 weeks. In contrast to these findings, rabbits given the sonicated immunotherapic did not show any protection and had an increase of 211.8% in the size of lesions. This failure of sonicated immunotherapic may reflect denaturation of protective antigens due to the sonication method.

Pitiose eqüina no Pantanal brasileiro: aspectos clínico-patológicos de casos típicos e atípicos

A pitiose eqüina é doença endêmica no Pantanal Brasileiro e causa prejuízos significativos a eqüinocultura. Neste trabalho são relatados 16 casos de pitiose subcutânea em eqüinos no Pantanal Sul-Matogrossense, que foram divididos em onze casos típicos e cinco casos atípicos, de acordo com o quadro clínico e o tempo de duração das lesões. O diagnóstico foi confirmado pela detecção de anticorpos específicos pelo teste ELISA, isolamento do agente e histopato-lógico. A duração da doença variou entre 1 e 6 meses nos casos típicos e superior a 12 meses nos casos atípicos. As lesões dos casos típicos caracterizavam-se por granulomas subcutâneos, ulcerados, com abundante secreção serossangui-nolenta e prurido. Nos casos atípicos foram observadas lesões subcutâneas caracterizadas por grandes massas "tumorais" circunscritas, recobertas por pele escura, sem ulcerações e com pouca secreção. Os animais estavam em bom estado nutricional e as lesões apresentavam-se de aspecto organizado, às vezes pedunculadas. Histologicamente, foi observado tecido de granulação com muitos eosinófilos nos casos típicos, enquanto os atípicos, se caracterizaram por hiperplasia pseudo-epiteliomatosa da epiderme e infiltrado eosinofílico. As características clínicas e histopato-lógicas completas das duas formas clínicas e os possíveis fatores responsáveis pelas diferenças entre as duas formas são apresentados e discutidos.