Duodenal obstruction caused by infection with Pythium insidiosum in a 12-week-old puppy

Global Distribution and Clinical Features of Pythiosis in Humans and Animals

Pythiosis is a difficult-to-treat infectious disease caused by Pythium insidiosum. The condition is unfamiliar among healthcare workers. Manifestation of pythiosis is similar to other fungal infections, leading to misdiagnosis and delayed treatment. The geographical extent of pythiosis at a global scale is unclear. This study aimed to analyze the clinical information recorded in the scientific literature to comprehensively project epidemiological characteristics, clinical features, and future trends of pythiosis. From 1980 to 2021, 4203 cases of pythiosis in humans (n = 771; 18.3%) and animals (primarily horse, dog, and cow; n = 3432; 81.7%), with an average of 103 cases/year, were recruited. Pythiosis case reports significantly increased in the last decade. Pythiosis spanned 23 tropical, subtropical, and temperate countries worldwide. Some patients acquired pythiosis from a trip to an endemic country. Strikingly, 94.3% of human cases were in India and Thailand, while 79.2% of affected animals were in the U.S.A. and Brazil. Clinical features of pythiosis varied. Vascular and ocular pythiosis were only observed in humans, whereas cutaneous/subcutaneous and gastrointestinal infections were predominant in animals. Mortality depended on host species and clinical forms: for example, none in patients with ocular pythiosis, 0.7% in cows with a cutaneous lesion, 26.8% in humans with vascular disease, 86.4% in dogs with gastrointestinal pathology, and 100% in several animals with disseminated infection. In summary, this study reports up-to-date epidemiological and clinical features of pythiosis in humans and animals. It increases awareness of this life-threatening disease, as the illness or outbreak can exist in any country, not limited to the endemic areas.

Geographic distribution of Pythium insidiosum infections in the United States

OBJECTIVE

To describe the geographic distribution of infections caused by Pythium insidiosum in dogs, horses, and other animal species in the US.

ANIMALS

For the last 20 years, we have collected data from cases of pythiosis in 1,150 horses, 467 dogs, and other species (59) from various geographic locations in the US.

PROCEDURES

Due to lost data (from 2006 to 2016), the selected cases include years 2000 to 2005 and 2016 to 2020. The selection of cases was based on infected host clinical features, serum samples demonstrating strong positive anti-P insidiosum IgG titers in serologic assays, and positive results on ≥ 1 of the following diagnostic modalities: microbial culture on 2% Sabouraud dextrose agar, histologic evaluation, PCR assay, and wet mount cytologic evaluation (with potassium hydroxide).

RESULTS

Most confirmed P insidiosum infections were found in horses and dogs in the southeastern US. Interestingly, in Texas, no cases were found west of longitude 100°W. Few pythiosis cases were diagnosed in west-coast states. Equine cases were more often diagnosed during summer and fall months, but canine cases were more often diagnosed between September and February. Cases in other species were discovered in the same geographic areas as those in dogs and horses.

CLINICAL RELEVANCE

To our knowledge, this is the first report providing the ecological distribution of P insidiosum infection in affected species in the US. Results of this study illustrated the importance of including P insidiosum in the differential diagnostic scheme of nonhealing skin lesions or intestinal granulomatous masses, particularly in dogs and horses inhabiting or having visited endemic areas.

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.

Review of methods and antimicrobial agents for susceptibility testing against Pythium insidiosum

Pythiosis is a life-threatening infectious disease of humans and animals caused by the oomycete microorganism Pythium insidiosum. The disease has been increasingly diagnosed worldwide. P. insidiosum inhabits freshwater and presents in two forms: mycelium and zoospore. Clinical manifestations of pythiosis include an infection of the artery, eye, skin, or gastrointestinal tract. The management of pythiosis is problematic due to the lack of effective treatment. Many patients die from an uncontrolled infection. The drug susceptibility testing provides clinically-useful information that could lead to proper drug selection against P. insidiosum. Currently, no standard CLSI protocol for the drug susceptibility of P. insidiosum is available. This review aims at describing methods and antimicrobial agents for susceptibility testing against P. insidiosum. Several in-house in vitro susceptibility methods (i.e., broth microdilution method, radial growth method, and agar diffusion method) have been established for P. insidiosum. Either mycelium or zoospore can be an inoculum. Rabbit is the commonly-used model of pythiosis for in vivo drug susceptibility testing. Based on the susceptibility results (i.e., minimal inhibitory concentration and inhibition zone), several antibacterial and antifungal drugs, alone or combination, exhibited an in vitro or in vivo effect against P. insidiosum. Some distinct compounds, antiseptic agents, essential oils, and plant extracts, also show anti-P. insidiosum activities. Successfully medical treatment, guided by the drug susceptibility data, has been reported in some pythiosis patients. Future studies should emphasize finding a novel and effective anti-P. insidiosum drug, standardizing in vitro susceptibility method and correlating drug susceptibility data and clinical outcome of pythiosis patients for a better interpretation of the susceptibility results.

Single-incision, laparoscopic-assisted jejunal resection and anastomosis following a gunshot wound

A 2 yr old castrated male Pomeranian was evaluated for a 6 wk history of chronic vomiting, intermittent anorexia, and lethargy. Physical examination revealed a palpable, nonpainful, soft-tissue mass in the midabdominal area. Abdominal radiographs and ultrasound revealed a focal, eccentric thickening of the jejunal wall with associated jejunal mural foreign body and partial mechanical obstruction. Following diagnosis of a partial intestinal obstruction as the cause of chronic vomiting, the patient underwent general anesthesia for a laparoscopic-assisted, midjejunal resection and anastomosis using a single-incision laparoscopic surgery port. The patient was discharged the day after surgery, and clinical signs abated according to information obtained during a telephone interview conducted 2 and 8 wk postoperatively. The dog described in this report is a unique case of partial intestinal obstruction treated by laparoscopic-assisted resection and anastomosis using a single-incision laparoscopic surgery port.

Canine gastrointestinal pythiosis treatment by combined antifungal and immunotherapy and review of published studies

Pythium insidiosum is an oomycete, a fungal like microorganism, which infects mammals, causing pythiosis in animals and humans, especially in tropical and subtropical regions around the world. The treatment for this infection is very difficult, and therapeutic options commonly comprise surgery, immunotherapy and antimicrobial drugs. The present report describes the clinical healing of a dog with gastrointestinal pythiosis by treatment with a combination of antifungals and immunotherapy, as well as reviews the cases reported in the literature that used some type of therapy for canine pythiosis. A 2.5-year-old male beagle initially showed sporadic vomiting episodes, and this symptom became more frequent 5 months after the onset of clinical signs. Celiotomy procedure found thickness of the stomach wall extending to the pylorus and duodenum. A biopsy was performed, and the diagnosis of pythiosis was made by mycological, histopathological analyses and molecular identification. Therapy was based on an association of terbinafine plus itraconazole during 12 months and immunotherapy for 2.5 months. The healing of the dog reported here allows us to propose the use of immunotherapy associated with antifungal therapy to treat canine gastrointestinal pythiosis. However, additional studies should be performed on a larger number of patients to establish a standard treatment protocol for canine pythiosis.

Gastric pythiosis in a dog

BACKGROUND

Pythiosis is caused by the agent Pythium insidiosum, an aquatic oomycete of the kingdom Stramenopila.

AIMS

To describe the symptoms, pathological changes and diagnosis methods of gastric pythiosis in dogs.

METHODS

A three-year-old female German shepherd, with access to wetlands, was attended due to vomiting and recurrent diarrhea of 30 days of duration. A palpable mass in the abdomen filling the left epigastric region was identified in the clinical examination. Simple and contrasted radiological examination and ultrasound of abdominal cavity were performed. The animal was referred for exploratory laparotomy for the removal of the mass. The extent of the mass prevented from the excision and the animal was euthanized. Samples of the tumor mass were collected and sent for morphological study and immunohistochemistry.

RESULTS

The changes observed in imaging studies were consistent with gastric pythiosis. In cytology and histopathology, non-septate hyphae were identified, and in immunohistochemistry a strong positivity of anti-Pythium antibodies was observed, confirming the diagnosis of pythiosis.

CONCLUSIONS

Pythiosis in dogs is diagnosed late and tends to evolve in the animal's death. The definitive diagnosis is by cytology, histology and immunohistochemistry.

Obstrução intestinal por Pythium insidiosum em um cão: relato de caso

Relata-se um caso de pitiose intestinal em um Husky Siberiano, de um ano de idade, macho atendido em um Hospital Veterinário Escola com sinais de obstrução intestinal. Ao exame físico, notou-se massa cilíndrica na região abdominal cranial, posteriormente confirmada por meio de radiografia e ultrassonografia. Durante a laparotomia exploratória, constatou-se massa extraluminal envolvendo o jejuno e alterações na parede do órgão. Realizou-se a ressecção da porção afetada do intestino e, posteriormente, anastomose. O exame histológico do tecido evidenciou inflamação piogranulomatosa acentuada. Na coloração de prata metenamina de Grocott, hifas septadas foram observadas. O diagnóstico de infecção por Pythium insidiosum foi confirmado por meio da imunoistoquímica. Após a cirurgia, o animal restabeleceu a defecação; no 30° dia pós-cirúrgico, foi relatada ainda presença de diarreia. O tratamento com itraconazol e terbinafina foi instituído durante 60 dias. Após dois anos do procedimento cirúrgico e do tratamento com antifúngicos orais, o cão não apresentou recidiva.

Aspectos clínicos, morfológicos e imuno-histoquímicos da pitiose gastrintestinal canina

Através de um estudo retrospectivo dos casos de biópsias e necropsias de cães recebidos no Laboratório de Patologia Veterinária da Universidade Federal de Santa Maria, constatou-se a ocorrência de dois casos confirmados e de quatro casos suspeitos de pitiose gastrintestinal canina. Os dois casos diagnosticados e publicados tiveram a etiologia confirmada através da cultura e indução de zoosporogênese ou por nested-PCR. Neste estudo utilizou-se a técnica de imuno-histoquímica com anticorpo policlonal anti-Pythium insidiosum para confirmação da etiologia dos quatro casos suspeitos. A epidemiologia, sinais clínicos, lesões macroscópicas e microscópicas, características histoquímicas e imuno-histoquímicas e diagnósticos diferenciais são relatados e discutidos.

Human pythiosis, a rare cause of arteritis: case report and literature review

OBJECTIVE

To present a case of Pythium insidiosum arteritis and review reported cases of human pythiosis.

METHODS

Search of MEDLINE (PubMed) and the Thai Index Medicus was performed using the words "pythiosis" and "pythium." Search of abstracts from a scientific meeting also was performed. Only reported cases in the English or Thai language, with enough clinical information for analysis, were included.

RESULTS

There were a total of 32 cases of human pythiosis, with 31 identified in the literature. Twenty-five cases were Thai. Twenty of 21 patients with known occupations were farmers. There was ocular infection in 9 cases, subcutaneous infection in 5 cases, arterial infection in 17 cases, and cardiopulmonary infection in 1 case. Thalassemia was a common associated finding. In addition to systemic antifungal therapy, surgery was required in most cases. The highest mortality rate was seen in the arteritic form, particularly in patients with arterial lesions proximal to the superficial femoral artery.

CONCLUSIONS

Human pythiosis is rare. Physicians should be suspicious of pythiosis in individuals, particularly farmers in Thailand, who develop nonhealing cutaneous ulcers or keratitis, which do not respond to conventional treatment. P insidiosum infections should be listed as a rare cause of infectious arteritis.