Gary Bauer, 11 Dec 2024. Botswana’s mass elephant die-off: Scientists discover cause Erik Verrynne, 11 Dec 2024 This remains speculation. My comments: I am not convinced about the Cyanobacteria conclusion, especially based on remote sensing techniques: 1. Other animals and species that used the waterholes were not affected, including cattle that we were herding in the area at that time 2. There were elephant mortalities on the flood plains in flowing water where it was highly unlikely for a algae bloom to build up 3. The few post-mortem examinations did not show normal symptoms of Microcystis toxicity, nor could the histopathology confirm without doubt any cyanotoxin involvement. It was mentioned as a potential DD on very poorly preserved tissue samples. Microcystis is the only Cyanobacterial toxic bloom that have ever been confirmed in freshwater outbreaks in Southern Africa (that was in the Kruger National Park outbreak), although other suspected cyanotoxins were regularly reported. 4. There was no confirmation of cyanotoxins in testing of the submitted water samples 5. The algae growth that has been seen with NDVI in this article is a common occurrence at the beginning and end of the rainy season and does not appear to be toxic. 6. The cattle that we herded in the area during that time would walk through it and drink the water without any ill effects. 7. Even though the mortalities affected animals of all ages and sexes, it did not kill a significant section of families but only relatively small number of individuals in the family herds. One would have expected that more members of a family would have been killed, since all but the small calves would be drinking and be exposed. 8. Some carcasses were found dead in the waterholes, again highly unlikely for algae blooms to be so toxic that it would cause that degree of peracute deaths. If so, it reinforces the contradiction in point 6. 9. I flew over the area during the time and although I did not record it, my first impression was a directional tendency of the carcasses towards the water holes and not away from the water as would be expected after a water source toxicity. This raises a concern about the value of remote sensing articles in the absence of verification on the ground, especially when it comes to disease and mortality investigations. In the absence of confirmation of a direct link between a disease agent and its affected host, even in the presence of a potential vector or reservoir, a diagnosis remains speculative. I personally believe the connection with the waterholes was “thirst” as a symptom. The presence of an infectious agent that affected some immunocompromised individuals within the population and then allowed the population to build up immunity would far better satisfy the epidemiological profile of our observations on the ground. Roy Bengis, 11 Dec 2024 Very well stated Erik, I have similar reservations for exactly those reasons. Jacoba Donga, 11 Dec 2924 Erik. Thanks for sharing your first-hand experience and insight. Nodularia was implicated in the Western Cape in deaths of sheep, cattle and a dog. Nodularia was dominant blue-green algae in 2 outbreaks affecting cattle and sheep, no toxin analysis. The dog case was based on the dominance of Nodularia in the bloom and nodularin in the water, and histopathology. Erik Verrynne, 11 Dec 2024 Thanks Jacoba. My apologies. I was referring to wildlife cases. I am aware of the livestock cases at Malmesbury and Darling in 1994 and I reviewed it as part of my presentation. The Nodularia toxins were not isolated though. Neither were the Oscillatoria toxins in the published outbreak in July 2008 in the Limpopo (Oberholster et al 2009).
