Coccidioides immitis mastitis in a mare

Coccidioidomycosis in 26 horses in California, USA: case series and review of the literature

Coccidioidomycosis is a fungal disease caused by Coccidioides immitis or Coccidioides posadasii. We searched the records of the California Animal Health and Food Safety Laboratory from 1990 through 2020 for cases of coccidioidomycosis in horses. The selection criteria for these cases were: 1) live-born horses submitted for autopsy, and 2) a diagnosis of coccidioidomycosis was established, regardless of cause of death. During that time, 19,054 horses were received, and 26 cases (0.14%) of coccidioidomycosis were diagnosed in horses, of which 19 (73%) cases had pneumonia and/or pleuritis with or without lesions in other organs, and 7 (27%) cases had lesions only in organs other than the lungs (nasal mucosa, spleen, thoracic lymph nodes, heart, pericardial sac, liver, kidney, mediastinum, and/or mesentery). Pneumonia was diagnosed as the cause of death in 1,838 (9.64%) of the horses received; Coccidioides spp. was the cause of pneumonia in 19 (1.0%) of these animals. Horses have been reported to have low susceptibility to coccidioidomycosis, and the severity and chronicity of the disease can be variable. Lesions in our cases consisted of multifocal-to-coalescing pyogranulomas with intralesional fungal spherules. Coccidioidomycosis must be considered a differential diagnosis in cases of persistent cough, chronic weight loss, fever, and cases with a travel history to, or living in, a region considered endemic for coccidioidomycosis. Coccidioides spp. infection should also be considered when pyogranulomatous inflammation is found within lung, spleen, nasal mucosa, and lymph nodes of horses.

Antimicrobial Selection for the Equine Practitioner

Antimicrobial drugs play an important, often central, role in the therapeutic management of mature horses and foals with a variety of illnesses, including those requiring critical care. Antimicrobial use must be based on rational principles involving thorough patient evaluation and sound clinical judgment that indicate a high likelihood that the patient has a bacterial infection and that antimicrobials are indicated to promote recovery. The aim of antimicrobial treatment is to inflict an insult on infecting bacteria sufficient to kill the organism or render it susceptible to inactivation by natural host defenses or the local microenvironment without adversely affecting the patient.

Development and Pathology of the Equine Mammary Gland

An understanding of the anatomy, histology, and development of the equine mammary gland underpins study of the pathology of diseases including galactorrhoea, agalactia, mastitis, and mammary tumour development. This review examines the prenatal development of the equine mammary gland and the striking degree to which the tissue undergoes postnatal development associated with the reproductive cycle. The gland is characterised by epithelial structures arranged in terminal duct lobular units, similar to those of the human breast, supported by distinct zones of intra- and interlobular collagenous stroma. Mastitis and mammary carcinomas are two of the most frequently described equine mammary pathologies and have an overlap in associated clinical signs. Mastitis is most frequently associated with bacterial aetiologies, particularly Streptococcus spp., and knowledge of the process of post-lactational regression can be applied to preventative husbandry strategies. Equine mammary tumours are rare and carry a poor prognosis in many cases. Recent studies have used mammosphere assays to reveal novel insights into the identification and potential behaviour of mammary stem/progenitor cell populations. These suggest that mammospheres derived from equine cells have different growth dynamics compared to those from other species. In parallel with studying the equine mammary gland in order to advance knowledge of equine mammary disease at the interface of basic and clinical science, there is a need to better understand equine lactational biology. This is driven in part by the recognition of the potential value of horse and donkey milk for human consumption, particularly donkey milk in children with 'Cow Milk Protein Allergy'.

Novel canine anti-Coccidioides immunoglobulin G enzyme immunoassay aids in diagnosis of coccidioidomycosis in dogs

The diagnosis of coccidioidomycosis (CM) in dogs is typically based on clinical presentation, serology, and (less frequently) spherule identification. Agar gel immunodiffusion (AGID) is the most commonly employed serological method, but AGID is slow (requiring up to a week for titer). A Coccidioides antigen enzyme immunoassay (EIA) is also available; however, sensitivity is low in CM dogs. An antibody EIA was developed to detect canine immunoglobulin G (IgG) reacting to Coccidioides antigens. Serum was evaluated from dogs with pathology proven CM and/or AGID positive CM, as well as dogs with histoplasmosis, blastomycosis, non-fungal infections, or healthy dogs. A standard curve was used to convert optical density (OD) values into EIA units (EU). Serum and urine samples from CM dogs were also tested in the antigen EIA. Sensitivity and specificity for IgG were 89.2% and 97.2%, respectively, upon evaluation of dogs with proven or probable CM and control dogs. Cross-reactivity was observed in 7.7% and in 6.4% of dogs with histoplasmosis or blastomycosis, respectively. The antigen EIA alone was insensitive (33.8%). Combined IgG and antigen testing increased sensitivity to 93.2%, as three dogs were IgG-negative but had detectable serum or urine antigen. In 22 dogs with proven CM, sensitivity was statistically similar for antibody EIA and AGID (86% and 73%; P = .487). The MiraVista® canine Coccidioides antibody IgG EIA may aid in the diagnosis of CM by improving turnaround time with comparable sensitivity to AGID. Serial or concurrent testing by antibody and antigen EIAs may be beneficial when screening dogs for CM.

The habitat of Coccidioides spp. and the role of animals as reservoirs and disseminators in nature

BACKGROUND

Coccidioidomycosis, a potentially fatal fungal infection, is considered an emergent mycotic disease because of the increased incidence of fungal infections registered over recent years. Infection occurs through the inhalation of arthroconidia from two main species of Coccidioides: Coccidioides immitis and C. posadasii, which are both endemic to arid and semi-arid regions of North America. Coccidioides species not only infect humans but can also infect other mammals (land, aquatic, wild or domestic), reptiles and birds.

OBJECTIVE

To obtain information regarding the habitat of Coccidioides spp. and the animals infected by this fungus and to identify the role that infected animals play as reservoirs and disseminators of this fungus in nature.

MATERIALS

A literature review was conducted to identify the habitat of Coccidioides spp. and the infected non-human animal species targeted by this fungus.

RESULTS AND CONCLUSIONS

This review allows us to suggest that Coccidioides spp. may be classified as halotolerant organisms; nevertheless, to perpetuate their life cycle, these organisms depend on different animal species (reservoirs) that serve as a link with the environment, by acting as disseminators of the fungi in nature.

Fungal diseases of horses

Among diseases of horses caused by fungi (=mycoses), dermatophytosis, cryptococcosis and aspergillosis are of particular concern, due their worldwide diffusion and, for some of them, zoonotic potential. Conversely, other mycoses such as subcutaneous (i.e., pythiosis and mycetoma) or deep mycoses (i.e., blastomycosis and coccidioidomycosis) are rare, and/or limited to restricted geographical areas. Generally, subcutaneous and deep mycoses are chronic and progressive diseases; clinical signs include extensive, painful lesions (not pathognomonic), which resemble to other microbial infections. In all cases, early diagnosis is crucial in order to achieve a favorable prognosis. Knowledge of the epidemiology, clinical signs, and diagnosis of fungal diseases is essential for the establishment of effective therapeutic strategies. This article reviews the clinical manifestations, diagnosis and therapeutic protocols of equine fungal infections as a support to early diagnosis and application of targeted therapeutic and control strategies.

Comparison of Coccidioides immitis serological antibody titres between forms of clinical coccidioidomycosis in horses

A retrospective study was performed to determine if there is an association between serological Coccidioides immitis antibody titres (IgG) and form/severity of coccidioidal disease in horses, and to identify trends in survival and treatment success based on the form of the disease. Data were obtained on horses with positive serological titres tested at the Coccidioidomycosis Serology Laboratory, School of Medicine, University of California, Davis from 1981 to 2004. Thirty-nine cases in which a diagnosis of coccidioidomycosis had been made were selected for inclusion. Six distinct categories were identified including abortion (n=6), miliary/interstitial pneumonia (n=6), pneumonia with thoracic effusion (pleural or pericardial) (n=11), disseminated (n=10), osteomyelitis (n=3) and external abscessation (n=3) both without pulmonary disease. Statistical differences in titre distribution were found between the abortion category and the pulmonary category (P=0.003), the abortion category and pneumonia with thoracic effusion (P=0.001), the abortion category and disseminated disease (P=0.001), and the pulmonary form and pneumonia with effusion (P=0.001). The other categories had overlapping titre results. Higher serological antibody titres seemed to be associated with a poorer prognosis for survival. Categories with the highest titres, disseminated (geometric mean titre=104) and pneumonia with thoracic effusion (geometric mean titre=226), were overwhelmingly fatal (19/21 known deaths) due to severe clinical disease. The categories with lower titres, abortion (geometric mean titre=4), bone involvement only (geometric mean titre=13) and cutaneous (geometric mean titre=5), had a better survival rate (10/12 known survivors) and less severe clinical disease. Measurement of serological titre may be a useful diagnostic aid in establishing form and severity of disease and thus inform prognosis.

Seroprevalence of antibodies against Coccidioides immitis in healthy horses

OBJECTIVE

To determine the seroprevalence of antibodies against Coccidioides immitis in healthy horses residing in an area in which the organism is endemic.

DESIGN

Prospective study.

ANIMALS

197 healthy horses (in which coccidioidomycosis had not been previously diagnosed) that resided in an area of Arizona in which coccidioidomycosis is endemic.

PROCEDURE

Of the horses evaluated at the Arizona Equine Medical and Surgical Center during a 6-month period, 197 with no clinical signs of coccidioidomycosis were randomly selected for inclusion in the study; sera were evaluated for IgM and IgG antibodies against C immitis via an immunodiffusion assay (IgG-positive samples were assessed quantitatively). Within 6 months, recheck titer evaluations were attempted for all seropositive horses.

RESULTS

Serum antibodies against C immitis were detected in 8 of 197 horses (seroprevalence, 4.06%). Results of serologic assays were positive for IgG antibodies and negative for IgM antibodies in 7 horses and positive for both IgG and IgM antibodies in 1 horse; reciprocal serum IgG antibody titers were low (none > 8). Follow-up serologic data were obtained from 5 horses; compared with initial findings, horses had become seronegative or titers were unchanged or decreased. Duration of residence in the area was significantly shorter for seropositive horses than for seronegative horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum antibodies against C immitis may rarely be detected in healthy horses residing in an area in which the disease is endemic; any horse with a detectable serum antibody titer should be reevaluated after an interval of at least 3 weeks.

Pulmonary coccidioidomycosis in a neonatal foal

A 13-day-old foal with profound tachypnoea and respiratory distress was examined. Thoracic radiographs revealed a severe, diffuse miliary pattern, and the foal was markedly hypoxaemic. It failed to improve with empirical treatment, and was euthanased. Lesions associated with Coccidioides immitis infection were identified at postmortem examination, and were limited to the lower respiratory tract.