Epidemiology of systemic mycoses in Texas
Carlos Rodriguez, Epidemiology and Informatics Manager
The Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) assists Texas veterinarians in diagnosing an average of over 350 cases of systemic fungal infection each year. To do so, TVMDL offers serologic testing specific for Aspergillus, Blastomyces, Coccidioides, Cryptococcus, and Histoplasma. Additionally, these fungal pathogens may be cultured, or found via microscopic examination of blood smears, cytology specimens, and tissue biopsies. Using TVMDL testing data gathered from Texas animals since March 2019, this article briefly covers the frequency and distribution of the most common fungal diagnoses in Texas.
Out of 1,836 positive systemic mycosis cases since 2019 (Table 1), 1,648 (90%) were in samples collected from cats and dogs. Canine coccidioidomycosis accounted for over two-thirds of all positive fungal cases over this period (largely determined by serologic testing); of note, dogs made up 99% of Coccidioides diagnoses and were the only species in which rare Blastomyces infections were found. Cats accounted for 64% of Cryptococcus cases and 62% of Histoplasma cases, though a handful of feline Aspergillus and Coccidioides cases were also found. Two-thirds of Aspergillus cases originated in birds; dogs were the second most common species affected by Aspergillus, making up 22% of cases.
| Taxonomy | Aspergillus | Blastomyces | Coccidioides | Cryptococcus | Histoplasma | Total |
| Avian | 150 | 0 | 0 | 0 | 0 | 150 |
| Canine | 49 | 11 | 1,258 | 18 | 95 | 1,431 |
| Equine | 10 | 0 | 2 | 5 | 0 | 17 |
| Feline | 1 | 0 | 7 | 48 | 156 | 217 |
| Other | 10 | 0 | 5 | 4 | 2 | 21 |
| Total | 225 | 11 | 1,272 | 75 | 253 | 1,836 |
Table 1: Number of cases of each common systemic mycosis, broken down by patient species.
The map below shows the distribution of each of the 4 most common systemic fungal pathogens (excluding Blastomyces) within Texas. Each color represents a different fungal agent; the number of dots within a county represents the number of cases within that county. It should be noted that the dots representing cases within each county are randomly placed and are not specific locations within that county. Each matching colored ring—called a directional distribution ellipse—represents the area in which approximately 2/3 of those cases are located in Texas.
Although positive cases were found in 76 counties throughout Texas, the distribution of Coccidioides cases (yellow) is primarily in the southwestern parts of the state; this coincides with the organism’s propensity for drier environments, something which makes it common in desert climates of the western United States. Despite having fewer total cases, Histoplasma (green) has the broadest, most central distribution throughout Texas (95 counties). Cryptococcus (dark blue) shows a similar distribution but is represented in the fewest counties (35). Aspergillus (light purple) was found in 44 Texas counties, and the distribution of cases is skewed eastward within the state.
To learn more about TVMDL’s systemic mycosis testing, and other offerings, visit tvmdl.tamu.edu or call 1.888.646.5623.
