About a month ago, I posted on the mysterious deaths of crocodiles in the Olifants river system in Kruger National Park, South Africa. A recent update indicates that the cause of the fatal pansteatitis outbreak is still unknown despite intensive study. An interdisciplinary research captured 11 live crocodiles and found that seven of them were afflicted by pansteatitis. This is a scary prevalence rate. The media release strangely refers to these cases as "infections," but this is probably not correct as pansteatitis is typically caused by environmental poisons (e.g., rancid fat from spoiled fish). The current theory is that the crocs are acquiring the poisoning from eating the carcasses of other afflicted crocs. The intervention park managers are attempting now is to burn the bodies of dead crocs recovered by rangers. So far, rangers have counted 130 crocodile carcasses in the park.
Here is a review of pansteatitis (and other diseases) in farm raised crocodiles (and ostriches), including a picture of the hardened yellow fat in crocodile tails. This hardening of the fatty tissue in crocodile tails impairs their mobility and therefore their ability to hunt. Crocs with pansteatitis therefore waste away and die of starvation. There is no specific indication in the articles of the state of the crocs bodies. Are they emaciated? Another posting on ProMedmail, including some details of the dam that may be a source of pollutants is here. The moderator asks the important question: Is anything else affected? No mention is made in any of the news articles. What about other aquatic organisms in the Olifants River? For example, what about Cape Clawless Otters (Aonyx capensis)?
Crocodiles have been dying in large numbers on the Olifants River in Kruger National Park, the crown jewel of the South African Parks System. The article rather casually states that the die-off is attributable to environmental pollutants:
There is growing consensus that the croc die-off is a result of a confluence of low level toxins, which has lead to endocrinal [sic] abnormalities (that is, hormonal changes) in croc tissues.
As the moderator for the promedmail wrote, however, it would be nice to have some specific details explaining why this consensus is apparently growing:
The article does not specify chemicals, pesticides, or heavy metals, or their amounts, yet the article boldly states, "Long term exposure to these and other toxins may well be conspiring towards the crippling condition suffered by Olifants River crocodiles." So apparently, the specifics of the chemicals, pesticides and/or heavy metals are known. It would be much more beneficial to publish what has been found and the levels of those alleged toxins, then those doing research or having experience in the area would be able to suggest a possible solution.
It certainly seems possible, particularly given the diversion of water from the Olifants River and from new mining operations in Mozambique, but it would still be nice to have some more details. One of the striking features of the dead crocs is the fact that they have hardened yellow fat deposits in their tails. The article suggests that cause of death is pansteatitis, a disease caused by excessive consumption of unstabilized polyunsaturated fatty acids (often found in rotting fish). There is no evidence of correspondingly large fish die-off, which could complete the causal story. How the environmental contamination story fits in with pansteatitis seems an important missing link in understanding this problem.
Cattle that eat threadleaf groundsel can die of a disease that induces hard yellow liver, providing more suggestive evidence that an environmental poison might be responsible for the croc die-off. Maybe...?
This is a disturbing story, the resolution of which I will follow closely.