Parasitism of the respiratory system is a relatively common finding in stranded cetaceans, however, no systematic investigations regarding the severity, distribution, and clinical consequences of these infections in bottlenose dolphins have been conducted previously. This study determined the prevalence of lungworm infections in dead stranded (n=22) and live bottlenose dolphins (n=44) from southwest Florida during 2003-2005. Dead stranded bottlenose dolphins were necropsied, and lungs were examined visually, by palpation, and histologically for lesions consistent with verminous pneumonia. When present, nematodes were counted, measured, and identified to species based upon their morphology. Dolphin feces and blowhole swabs were collected and examined for nematode larvae. Lungworm prevalence was 77% in dead animals (n=22). The lesions in most cases were mild, chronic, and not the primary cause of death. Only 13% of dead animals examined had patent infections with larvae present in blowhole and fecal cytology, and only 18% of animals had intact worms present at necropsy with a geometric mean intensity of infection of 22.6 worms/animal. Intact worms were identified as either Halocercus lagenorhynchi or Skrjabinalius cryptocephalus. The highest prevalence of active infections was found in neonates and calves, including one stillborn calf. For free-ranging animals, all blowhole swabs (n=44) were negative, and fecal cytology (n=22) showed a 3% prevalence of patent infection. Findings from this study support the theory that bottlenose dolphins can be infected transplacentally by lungworms. The impact that such infections may have on neonatal survival is unknown; however, these infections could increase neonatal mortality.
This project was funded by a grant awarded from Harbor Branch Oceanographic Institution’s “Protect Wild Dolphins” program.