Say It Isn't So

A mystery is beginning to unfold here in Bonaire, Netherlands Antilles, and I must admit I'm not happy about the cast of characters. Beginning almost three weeks ago around the start of September, divers here began reporting unusual sightings of dead moray eels along the reef. Dead morays were also being spotted washed-up on the beaches of the marine park. Casualties do not at this time appear to be limited to any single species of moray. Apparently Green morays, Caribbean Spotted morays, and Goldentail morays have been among the victims. At present, the body count appears to be approaching 15-25 observed dead eel specimens, but the marine park is a big place and the actual mortality may be orders of magnitude greater.

In talking with the Bonaire Marine Park Manager, it is not yet clear what might be the cause of this UMT (unusual mortality event). It could be any of a variety of causes ranging from bacterial to viral to fungal. Bonaire does not have a marine pathology facility on-island, and there presently is no protocol yet established for screening for potential pathogens in specimens. The nearest facility for performing this sort of analysis is located in the Greater Antilles in Puerto Rico. But getting dead specimens from the water to the lab is not a simple process.

Yesterday provides a telling example. During a morning dive, a dive master found a recently deceased Spotted moray resting near the reef drop-off. With good intention, he brought it back to the dive boat in hopes of delivering the eel to the marine park authority for study. But with no means of temporary preservation in this tropical heat, a dead eel specimen rapidly degrades from fresh cadaver to a stinky wind-sock of liquefied goo. We looked for something to place the specimen in, but the only available storage was a cooler where cold drinks were stored. Not knowing what possible agent is at work in the moray deaths, it would be ill-advised to store a potentially infectious corpse where human food is also stored.

It's been clearly established that many marine pathogens can be zoonotic, that is an infectious disease is able to be transmitted (usually by a vector) from animals, both wild and domestic, to humans. Four relatively common microbes––Brucella, Leptospira, Crytopsporidium, and Giardia--have been identified in commercially valuable marine fish. Ingestion of these pathogens can cause symptoms that include high fever, severe headaches, chills, muscle aches, vomiting, and diarrhea. Paralytic shellfish poisoning (PSP) or neurological shellfish poisoning (NSP), both caused by accumulated concentrations of algae-produced toxins, continue to afflict humans with seasonal outbreaks. Strains of a Brucella (a bacteria species) have been isolated from marine mammals and serological surveys suggest that exposure is widespread in dolphins and seals. The species has caused headaches, extreme fatigue, and severe sinusitus in marine mammal researchers. Other potential zoonotics include seal pox (occasionally causing painful nodules on the fingers of handlers) and Salmonella. A severe, painful bacterial infection associated with bite wounds, "seal finger", is also a hazard for handlers. Mycoplasma (a fungal species) have been implicated in its cause.

So in the interest of human safety, the dive master dumped the eel carcass overboard, and a potential treasure trove of scientific information was lost. Setting up proper protocols for handling potentially infectious specimens is not rocket science, but developing a well-articulated collection and storage protocol takes time and money. It's a function of resources and capacity to equip the entire marine tourism fleet here in Bonaire with the materials and training in how to handle dead marine specimens. Then of course there's the matter of analyzing the specimens. As I mentioned earlier, Bonaire lacks a marine pathology lab. Specimens must be quickly packaged and shipped cold but not frozen to a lab (specimens must not be allowed to freeze solid as expanding ice crystals in tissues will rupture cells and make histology difficult or impossible.)

Perhaps fortuitously, Steve McCullough is on-island this week as part of the Love Our Planet Week celebrations. Steve is founder and manager of the Marine Mammal Research and Conservation Center at the Harbor Branch Oceanographic Institute in Ft. Pierce, Florida. He's well-versed in UME protocols and the handling and study of marine mammal specimens that are found sick, dead, or dying. In fact, Steve was a busy man this week. In addition to his outreach and education responsibilities, he found himself called upon to perform a field inspection of a marine mammal stranding here as well. The first in possibly 12 years on Bonaire, he surveyed the decomposing remains of an as-yet unidentified toothed whale that washed-up on the east side of Bonaire.

Steve was able to advise the marine park authority on a cost effective and practical means of training Bonaire-based marine park staff on basic specimen preparation and analysis--from collection of specimens to rapid necropsy and sample collection. Rather than shipping an entire specimen to an out of country lab, basic tissue sampling and preservation can be performed in-country. While more precise microbiology and virology/toxicology may still need to be performed off-island, the speed in which specimens are prepared and a potential cause identified can be accelerated.

Since we are just three weeks-in on this moray UME, time is of the essence. The moray die-off may be just now manifesting itself and may be the first sign of a deeper problem affecting Bonaire's coastal habitats. Morays may be just one of many organisms that could be affected. Steve McCullough described an incident he witnessed in Florida a few years back where local crab fishers along the Indian River estuary first noticed a UME involving crabs. Dead crabs were just an early warning. The pathogen, a bacteria, rapidly worked its way up the trophic pyramid. In as little as one month, close to 35 Bottlenose dolphins that hunted within the estuary would eventually die of the same bacterial infection.

It's far too early to even speculate on a potential infectious agent in the moray UME. But it's worthwhile to keep in mind that marine pathogens can flow in two directions. I've already mentioned that zoonotics can create links that flow from marine organisms to humans. But reverse zoonosis can also occur where human or terrestrial pathogens can be transmitted to marine life. Dogs and cats may suffer Salmonellosis that has been positively correlated to localized outbreaks in marine mammal populations such as Harbor or Fur seals. In Monterey Bay, California, outbreaks of Toxoplasmosis (a protozoa) in Sea otter populations has been traced to kitty litter that finds its way into land fills or storm drains and works its way up the marine food chain.

Perhaps of greatest concern is the growing evidence that contamination of coastal waters from treated and untreated sewage discharge or rainwater and river runoff raises concerns that marine animals can act as reservoirs for bacteria—acquiring and maintaining antibiotic-resistant genes and then multiplying and spreading them to other marine life. Where does the antibiotic-resistance come from? From our almost ubiquitous overuse of antibiotics in everything from medicine to beef, poultry, and pork farms, to agriculture.

That's a scary prospect for Bonaire, where "healthiest reefs in the Caribbean" is almost the national motto. I'll be following the developments closely and look forward to hearing what insight researchers find.