The presence of diatom algae in a tracheal wash from a German Wirehaired Pointer with aspiration pneumonia

Abstract

A 7-year-old spayed female German Wirehaired Pointer was presented with difficulty breathing after being found seizing in a water-filled drainage ditch while out hunting. Aspirates from a tracheal wash contained numerous degenerate neutrophils, fewer macrophages, some of which contained basophilic debris, low numbers of extracellular diatoms, and a single intracellular short bacterial rod. As the dog continued to clinically decline and could not be weaned from oxygen support, the owners chose euthanasia. The major necropsy finding was a severe granulomatous bronchopneumonia that was likely due to aspiration of foreign material based on the microscopic presence of plant-like material, bi-refringent crystalline material, non-cellular debris, and occasional fungal structures. Diatoms are a class of algae that live primarily in water. Diatom analysis has been used, with some controversy, in human forensics to assist in documenting drowning as the cause of death. In this case, given the clinical history, the presence of diatoms and inflammation in the tracheal wash were interpreted as a likely result of the aspiration of surface water. To our knowledge, this is the first reported case of diatoms observed in a cytologic specimen in a nonhuman mammal with aspiration pneumonia.

Diatoms in cytologic specimens of aquatic animals – Part I, fecal samples

“…However, the diagnostic use of embolized diatoms in various tissues to diagnose forced submergence is controversial since diatoms can be present in tissues without drowning. In veterinary medicine, one recent case of freshwater aspiration pneumonia in a dog was confirmed by diatom identification in tracheal and lung washes …”

Veterinary Forensic Pathology

“…25 As diatoms have been found in bodies not recovered from water and in living people, the possibility that they enter the circulation from ingested food must be considered. 91 Although diatoms were identified in the tracheal wash of a dog that aspirated during a seizure in a water-filled drainage ditch, 6 application of the diatom test to confirm drowning in animals requires additional rigorous validation studies.…”

“…91 The use of diatoms as a diagnostic test for drowning is based on the assumption that the individual must be alive for them to be aspirated, penetrate the alveolar-capillary membrane, enter the circulation, and enter tissues including marrow. 6,74 If meticulous and usually time-consuming techniques are used to retrieve diatoms, usually from the bone marrow, their presence in large numbers may corroborate a diagnosis of drowning, and their unique characteristics may identify the location and drowning medium of the victim. The sensitivity of the method is relatively low and depends on the time of year when the algae bloom.…”

“…30 Level of consciousness upon presentation, even coma, was not associated with outcome. 30 Complications in animals that survive drowning include reduced mentation or neurological deficits, 51 noncardiogenic pulmonary edema, 29 septic pneumonia, 6 and acute respiratory distress syndrome. 30 …”

“…An estimated 388000 people drown annually and it is the third leading cause of accidental death worldwide. 66 The peerreviewed veterinary literature on accidental and nonaccidental drowning in animals is scarce, 1,6,28,31,58,60 although the topic is covered briefly in several veterinary forensic textbooks. 18,50,59 Accidents while in water including electrical shock, entrapment, entanglement, and neurologic dysfunction such as ataxia and epilepsy are reported in animals that have drowned, or have been resuscitated following rescue from water.…”