Cetacean Strandings in Costa Rica 2004–2020: A Review of Marine Brucellosis Findings
Abstract
A total of 179 cetaceans from 21 species have been reported stranded on the Costa Rican shorelines from January 2004 to December 2020. From these, 96.6% (n=173) were reported stranded on the Pacific coast and 3.3% (n=6) on the Caribbean coast. These animals belonged to five different families, including Balaenopteridae, Physiteridae, Kogiidae, Ziphiidae, and Delphinidae.1
Striped dolphin (Stenella coeruleoalba) is the most frequently stranded species, representing 43.5% (n=78) of the total cases. Complete necropsies were performed on 75.6% (n=59) of these dolphins, and Brucella ceti ST26 was isolated from cerebrospinal fluid (CSF) in 71.2% (n=42).2 Meningoencephalitis with increased cerebrospinal fluid volume and opacity with secondary hydrocephalus continues to be the most common presentation.3-5 Following the standard protocols for postmortem computed tomography neuroimaging, these animals present different levels of enlargement of the temporal horns of the lateral ventricles with accumulation of CSF.6 Brucella ceti ST26 was also isolated from CSF, brain tissue, and atlanto-occipital joint from an individual common dolphin (Delphinus delphis) and from lungworms (Halocerchus spp.) from four striped dolphins.4,7
During this time, two striped dolphins and one dwarf sperm whale (Kogia sima) were reported as pregnant females, and placentitis was described in both species. Brucella ceti ST26 was isolated from the placenta, uterine fluids, milk, and calf of one of the striped dolphins; meanwhile, a marine Brucella ST27 was isolated from the K. sima and its calf.8 Individuals from other species have been reported as seropositive animals in the country; however, Brucellae were not cultured from them.5,7 These species include: blue whale (Balaenoptera musculus), Cuvier’s beaked whale (Ziphius cavirostris), bottlenose dolphin (Tursiops truncatus), rough tooth dolphin (Steno bredanensis), pantropical spotted dolphin (Stenella attenuata), Risso’s dolphin (Grampus griseus) for the Pacific shorelines, and Fraser’s dolphin (Lagenodelphis hosei) from the Caribbean coast.1
The combination of serology before a complete necropsy and bacteriology on freshly collected samples (in animals as code 2 and 3), as well as the use of the non-commercial selective medium with fewer antibiotics (CITA and Farrell’s medium), have been critical for the success of isolation of the Brucellae in these animals.9,10 Molecular techniques as MVLA-16 and whole-genome sequencing have been key tools for clustering the isolates according to host-geographical location.2 The real impact of mortality, either by reproductive failure or complications during the life span in the cetacean population with marine Brucella in the eastern tropical Pacific, is currently unknown since this clinical presentation has been reported in other oceanographic areas of the Pacific Ocean; however, laboratory capacity-building is needed to better understand this potentially zoonotic disease.
Acknowledgments
The authors thank the people who helped during stranding of cetaceans in coastal areas of Costa Rica: Coastguard, fire department, emergency service (911), SINAC, Parque Marino del Pacífico, personnel from PIET, Veterinary School, UNA and the National Service of Animal Health (SENASA), Costa Rica.
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