Pulmonary silicosis in 2 rock hyraxes, and literature review

A cross-sectional observational study of birefringent particulates in bronchoalveolar lavage cytology in horses with equine asthma from the West v East coasts of the USA

Equine asthma (EA) is an important cause of wastage in the USA horse industry. Exposure to organic particulates, from stable dust, airborne pollen, and fungal loads, is posited to be the main cause. Dust arising from the earth's crust has been largely ignored as a contributor to EA in the veterinary literature. The objectives of this study were to investigate the occurrence of birefringent particulates in the bronchoalveolar lavage fluid (BALF) of horses with a clinical complaint of EA residing in the arid West of the USA v. the East, in an effort to determine the contribution of geolocation to geogenic dust exposure. We analyzed BALF cytology and historical data sent to our referral clinical laboratory from 148 horses from the West Coast and 233 horses from the East Coast of the USA over a 6-year period, using light microscopy to determine cell proportions and other visible elements as well as a polarizing lens to detect birefringent material. Univariate analysis showed that horses from the West coast were significantly more likely to have birefringent particulates in the BALF than horses from the East coast (40.5% v. 8.6%, p < 0.001); while horses from the East had higher BALF neutrophil proportions. Horses from the West also had lower proportions of neutrophils in the BALF than those from the East (27.1 v. 10.9, p < .001). Using historical and BAL data in a forward stepwise binary logistic regression model with presence of birefringent particulates found within alveolar macrophages as the outcome, geographical location in the West retained significance as a predictor (OR 8.0, CI [4.3-14.8], p< .001). While the birefringent particulates cannot be identified on the basis of polarizing microscopy alone, this study provides evidence that horses from the West are exposed to inorganic particulates that may contribute to signs of equine asthma.

Silica and barium: Comparison of microscopic appearance and characterization of effects of silica on cytomorphology

BACKGROUND

Silica from plastic red top sample collection tubes and barium cause recognized artifacts in slide preparations for microscopic examination.

OBJECTIVES

The objectives of this study were to evaluate and directly compare the microscopic appearance of silica and barium particles and various slide preparation techniques (e.g., use of coverslips, oil immersion, and different stains). A secondary objective of this study was to evaluate the effects of silica particles on cellular morphology after mechanical trauma with cytocentrifugation.

METHODS

Fluid samples (deionized water, pleural effusion, peritoneal effusion, cerebrospinal fluid, and urine) were collected and evaluated in silica- and non-silica-containing tubes. Barium was added to silica and non-silica samples. Direct and cytocentrifuge preparations were compared to evaluate the effect of silica particles on cellular morphology. Preparations were stained with Wright-Giemsa, rhodizonic acid disodium salt, Alizarin Red, Grocott's methenamine silver, and Prussian blue.

RESULTS

Silica and barium particles were identifiable via light microscopy with and without polarized light, although silica particles diminished with immersion oil. Barium particles retained their structure and diminished less under oil. Cytoseal mounting medium for coverslip placement resulted in diminished refractility of silica and some barium particles. Silica particles with mechanical interaction during cytocentrifugation resulted in disrupted cellular morphology with many lysed cells. Silica and barium particles were negative for all special stains tested.

CONCLUSIONS

Silica from plastic red top tubes adversely affects cell morphology in cytocentrifuge preparations, potentially affecting manual differential cell counts and compromising diagnostic interpretation. Samples intended for microscopic evaluation should not be collected in silica-containing tubes.