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   This article is an abridged version of the original. The full article can be found in 3 parts and was first published in the Summer 2003, Winter 2004, and Summer 2004 issues of Bible and Spade. 

Did anthrax plague the Egyptians at the time of Moses and the Exodus of the Israelites? Anthrax is in the news a lot these days because of manmade bioterrorism. But naturally occurring outbreaks of the sheep-based disease go back thousands of years. Many Biblical scholars believe that the Biblical Ten Plagues were an interconnected series of catastrophic natural events that included an attack of anthrax on animals and humans.1 In the most widely known version of this theory published in 1957 by an English lit scholar named Greta Hort, the 'ecological domino' effect is kicked off by a massive 'red tide' of algae laced with anthrax bacteria in the Nile river, though there are many problems with the theory (e.g., scientists in Egypt and East Africa have never seen any trace of her 'naturally occurring' algae; anthrax is soil-based and not found in the Nile).2

Even if Hort's theory is not the correct one, a number of top specialists in the field of Harmful Algal Blooms (HAB's), such as leading U.S. expert Don Anderson of Woods Hole Oceanographic Institution, believe that some type of algae may have been behind the Plagues of Egypt. Former New York City chief epidemiologist John Marr has proposed a series of 'emerging new diseases' as not so new after all but as part of a chain of deadly biological Plagues in the time of the Israelite bondage. But there are many scientific as well as Biblical objections to such a naturalistic theory of the Egyptian Plagues.

According to Hort's theory, each Plague recounted in the book of Exodus occurs in the correct 'natural' sequence, all triggered by one underlying cause - a single and extraordinarily severe occurrence of the annual Nile flood in July. This torrent washed down a massive load of 'red' mud along with the main reddening agent, the red algae, which discolored and contaminated the water in a red tide (or an HAB, as biologists now prefer to call it). The supposedly red mud-algae together created the Plague of Blood. Hort names two species of algae as the culprits. Then followed the deadly chain reaction of successive Plagues, says Hort.

The algae killed the fish. Dead fish developed anthrax, sickening the frogs and driving them ashore. Dead frogs contaminated the soil, infecting and killing livestock animals with internal anthrax. Biting flies proliferated in the decaying plants left by the heavy flooding then carried the especially virulent skin anthrax from dead cattle to the live cattle and humans, causing the plague of 'boils.' The severe weather that had caused the unusual torrent then brought hail and locusts. The excessive load of mud from the high Nile flood dried into an unusually heavy covering of powdered silt. A violent dust storm lofted the silt into the air, creating an extraordinary darkness. The first fruits of crops were destroyed - rather than firstborn children - in the final Plague according to Hort, claiming error in translation of the Biblical account. Some of the Plagues may have missed the Israelites due to a natural sheltering effect of the Eastern Nile Delta valley they dwelled in, she claims. Hort suggests the Israelites left Egypt because they had food the Egyptians wanted and would have taken from them, so if they stayed they would 'die either by violence or starvation.'

In John Marr's theory a different set of organisms are identified in the events of the Ten Plagues using his experience in the science of epidemiology. He attributes the Blood Plague to Pfiesteria piscicida or the infamous 'cell from hell' that killed millions of fish in North Carolina in the 80's and 90's. This bizarre algae-like organism with its 50 different life cycles includes a deadly flesh-eating piranha-like stage that leaves fish bloody messes in the water - a 'Blood Plague' of sorts with actual blood, not red algae.3 Marr believes the toxic stages of the organism killed so many fish that normally feed on frogspawn that frogs proliferated in the Nile. Thus the Plague of Frogs. Because of the Pfiesteria toxins in the water the frogs were forced onto land to search for food, says Marr, but they quickly died because of those toxins. Without frogs to eat insects, now insects had a population explosion, resulting in Plagues of Lice and Flies. Livestock were then killed by a number of deadly viruses and bacteria carried by this excess number of insects. The Plagues of Hail and Locusts were just bad timing, says Marr.

So far so good, perhaps. But Biblical scholars may have some difficulty with Marr's proposal that the Plague of Darkness was actually a Plague of Blindness caused he says by the Rift Valley Fever which produces temporary blindness. And they may have even more trouble with the final Plague on the Firstborn which Marr claims was caused by a poisonous mold growing on the tops of the grain supplies infected by the locust plague. He thinks the firstborn were killed because they received extra portions of the food right off the top due to their privileged status and didn't realize it was contaminated with mycotoxins. Scholars object that there wouldn't have been any food left to contaminate after the previous plagues and Marr's ingenious theory doesn't explain such things as the Passover ritual.4

Hort's and Marr's theories are clever and convincing at first glance. However, it is well known that algae - even the strange Pfiesteria - mainly grow in stagnant bodies of water, not in free-flowing rivers.5 Red tides occur in slower-moving or becalmed saltwater oceans and estuaries rather than rivers (e.g., not one of the 1,109 worldwide Harmful Algae Events in the UNESCO database occurred in a freshwater river).6 These environments are very unlike the massive freshwater Nile, the second largest river in the world and clearly not a stagnant pond. It is common knowledge that plants need sunlight for photosynthesis, yet Hort's theory also requires massive loads of intensely dark silt that would kill her plant algae. It is most problematic that her 'red' algae are actually green and her 'red' Nile silt is actually brown, thus could not possibly have caused a red Plague of 'Blood.'

One of Hort's two culprit algae species is so far from being the cause of a deadly 'plague' that it is actually used today as a human food supplement which the present author has personally tested as safe. Neither species is toxic or a water pollutant rendering water undrinkable or unfit for consumption. Hort's algae are rare and fragile ice water species that belong in sub arctic cold climates, and can barely survive even in their own ideal environment let alone overwhelm a habitat, as Hort requires.7 It is a biological impossibility for these algae to survive in the tropical Nile. Exhaustive scientific studies have cataloged more than 400 species of algae in the Nile, and some 1,000 species in East Africa including Hort's alleged Lake Tana source, yet scientists have never found these two algae species there. In fact, no biologist in the history of science apparently has ever reported a red bloom of algae of any kind in the Nile or its headwaters, let alone of Hort's algae.

Anthrax cannot infect dead fish or live frogs as Hort claims. Anthrax only infects mammals, typically grazing herbivores such as sheep, cattle and goats, and does not infect frogs, amphibians, reptiles or fish.8 Anthrax is soil-based and isn't contracted in large bodies of water such as rivers. Biting flies have never been medically documented to spread anthrax to cattle or humans nor do they feed on dead animals. According to Hort these biting stable flies bred and spread disease in the Plague of Boils in early January. But these flies actually hibernate in winter in the pupa stage and do not mature until warm weather.9

Anthrax is a disease that mainly affects livestock animals such as sheep and cattle in agricultural regions, especially in the Third World, including the Middle East, but also in industrial nations that process cattle hides, leather and wool. It is caused by a rod-shaped bacterium, Bacillus anthracis, found in the soil that forms a tough dry covering or spore when exposed to air. The anthrax spore can survive for long periods up to 80 years or more under harsh conditions, a feature that has made it of special interest to designers of biological weapons. The egg-shaped spore is lifeless until it comes into contact with an animal or human. Then it bores into a white blood cell, multiplies, bursts the cell and spreads to other white blood cells and lymph nodes, attacking the immune system to repeat the process, like a bacterial version of the AIDS virus HIV only much more rapid. Victims develop fatal toxic shock from toxins emitted by the anthrax. Dead animals bleed into the soil where anthrax spores form and lie in wait for the next victims. The live or 'vegetative' anthrax bacilli are fragile and won't survive 24 hours outside an infected animal or human host unless turned into spores.10 Anthrax was named after the Greek word for coal, anthrakis, because of the black lesions formed on the skin.

Naturalistic theories of the Ten Plagues are popular as a way to avoid complete skepticism of the Bible on the one hand and complete supernaturalism by Divine miracle on the other. Bad bug theories may be due in part to a misnomer. A word such as 'plague' suggests only infectious disease when the actual multiple Hebrew words in the Bible refer more broadly to 'sharp blows' and 'calamity,' not just disease.


1. Greta Hort, "The Plagues of Egypt," Zeitschrift für die Alttestamentliche Wissenschaft, vol. 69 (1957) pp. 84-103; vol. 70 (1958) pp. 48-59; John R. Huddlestun, "Nile (OT)," in David Noel Freedman (ed.), The Anchor Bible Dictionary (Doubleday, New York, 1992) vol. 4, pp. 1108b-1112b; John H. Sailhamer, The Pentateuch as Narrative (Zondervan, Grand Rapids MI, 1992) p. 254; Kenneth A. Kitchen, "Plagues of Egypt," in James D. Douglas (ed.), New Bible Dictionary (Eerdmans, Grand Rapids MI, 1962) p. 1002; cf. R. Alan Cole, Exodus: An Introduction and Commentary [Tyndale Old Testament Commentaries] (Inter-Varsity Press, Downers Grove IL/Tyndale Press, London, 1973) p. 90; "Plagues upon Egypt," in Walter A. Elwell (ed.), Baker Encyclopedia of the Bible (Baker Book House, Grand Rapids MI, 1988) vol. 2, p. 1701. 

2. Julian Rzóska (ed.), The Nile, Biology of an Ancient River [Monographiae Biologicae vol. 29] (W. Junk B.V., The Hague, 1976). "Ecological domino theory" is the phrase used for Hort's theory in a Time magazine cover story. David van Biema, "In Search of Moses," Time, vol. 152, no. 24 (Dec. 14, 1998), online edition, p. 4, 

3. The recent attacks of the "cell from hell" Pfiesteria piscicida on fish in the coastal estuaries of North Carolina, Maryland, Virginia, Delaware and Florida are not technically fresh-water invasions as the brackish waters are in the confluence of oceanic salt water. See Univ. of Maryland Aquatic Pathobiology Center website, North Carolina State Univ. Aquatic Botany Lab website, North Carolina Dept. of Health & Human Services HAB Program website, and U.S. Environmental Protection Agency (EPA) website Despite the sensational Biblical-sounding title of the book on Pfiesteria by Rodney Barker, And the Waters Turned to Blood (Simon & Schuster, New York, 1997), the "blood" is that of the fish killed in the water, and not from the pigmentation of red-colored algae. Pfiesteria "does not cause visible 'red tides.' " Jack Greer, "In Harm's Way? The Threat of Toxic Algae," Maryland Marine Notes, vol. 15, no. 4 (July-Aug 1997) online edition at Nevertheless, a British Channel 4 television program "The Ten Plagues of Egypt" in the Equinox series, broadcast Aug. 18, 1998, and based on the research of epidemiologists John S. Marr and Curtis D. Malloy, has reportedly tried to explain the Plague of Blood as a Pfiesteria "red tide" attack even though the organism is not red. They claim that no toxic red tide algae that could occur in fresh water was known until a Pfiesteria attack in 1996, however those attacks were actually in salt water estuaries of rivers. Marr and Malloy attempt to create a series of interconnected Plagues caused by natural biological agents for the most part, just like Hort and subject to many of the same scientific and historical objections as Hort's theory. See: 

4. John Meakin at 

5. "HAB [Harmful Algal Bloom] events are commonly associated with stratified water columns, subject to long periods of low flow and little mixing," i.e., the stagnant pond effect. U.S. National Oceanic and Atmospheric Administration (NOAA) Coordinating Committee for Interagency Task Force on Harmful Algal Blooms and Hypoxia, "Integrated National Assessment of Harmful Algal Blooms" (rev. Oct. 22, 1999) online edition downloaded from, p. 15a. Esther Garcés, Mercedes Masá, Magda Vila, and Jordi Camp, "Harmful algae events in the Mediterranean: Are they increasing?" Harmful Algae News, no. 19 (May 2000) pp. 1, 10-11, at 1a-b, 11a (HAB's prefer calm tide less ocean). "'Red tides' are a coastal marine phenomenon.... The algae involved are species of Dinophyta [dinoflagellates] usually of the genera Gymnodinium or Gonyaulax which, having red pigments... impart a reddish tinge to the sea." Round, Ecology of Algae (1981) p. 307. IOC-UNESCO Harmful Algal Blooms Programme HAE-DAT (Harmful Algae Event Data Base). Cyanobacterial blooms in Australia prefer marine waters, warm stratified reservoirs and "very slow flowing" rivers. Glenn Shaw, "Cyanobacterial presentations at HAB 2000," Harmful Algae News, no. 19 (May 2000) pp. 2-3 at 2b-c.

6. Intergovernmental Oceanographic Commission-United Nations Educational, Scientific and Cultural Organization (IOC-UNESCO) Working Group on Harmful Algal Bloom Dynamics HAE-DAT (Harmful Algae Event Data Base) downloaded from, accessed July 2000. 

7. Ernest G. Pringsheim, "Nutritional Requirements of Haematococcus pluvialis and Related Species," Journal of Phycology, vol. 2 (1966) pp. 1-7 at 1-2, 5. 

8. USDA APHIS, "Anthrax" website, ibid., Nov. 2001; American Veterinary Medical Assoc. (AVMA), "Anthrax Fact Sheet," in Louisiana State Univ., Equine Health Studies Program, Equine Heath Studies Quarterly Newsletter, vol. 2, no. 1 (Summer 2001) online ed. at and; Burke A. Cunha, "Anthrax," eMedicine Journal, Nov. 29, 2001, vol. 2, no. 11, online at; UN FAO, "Anthrax in animals" (Dec. 2001). 

9. Hort's Stomoxys calcitrans biting fly is mentioned by scientists in East Africa but based on a mass of medical entomology and veterinary data it is never in connection with the spread of anthrax. Julian Rzóska and David J. Lewis, "Insects as Factor in General and Human Ecology in the Sudan," Nile/Biology (1976) pp. 330-331; see p. 208; Meryl Nass, "Anthrax Epizootic in Zimbabwe 1978-1980: Due to Deliberate Spread?" Physicians for Social Responsibility Quarterly, vol. 2 (1992) pp. 198-209, online ed. at, Prof. Burke A. Cunha, M.D., Director of Infectious Disease Fellowship, State Univ. of New York School of Medicine, and Chief, Infectious Disease, Winthrop Univ. Hospital, email to author, Feb. 26, 2002; Eastern Cereal and Oilseed Research Centre (ECORC) Research Branch, Agriculture and Agri-Food Canada, "Identification Systems for Biocontrol Insects (ISBI): Horn flies and stable flies," rev. Jan. 29, 2001, website info at tml; U.S. Dept. of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS), Veterinary Services, "Anthrax" information on website, rev. Nov. 2001, at 

10. Thomas V. Inglesby, et al., "Anthrax as a Biological Weapon," Journal of the American Medical Assoc. [JAMA], vol. 281, no. 18 (May 12, 1999) online ed. at; New Scientist "Anthrax Facts," website info, accessed Feb. 2002, at sp; David R. Bowen, Wayne State Univ. course, "GST 2020-Changing Life on Earth: Supplement for Agenda 7: Anthrax in the news and in this course," website info rev. Oct. 24, 2001, at; Randall K. Holmes, McGraw-Hill Harrison's Online Chapter 141 (2001) online at 

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