Dr John S. Marr, for many years the chief epidemiologist at the New York City Department of Health, and Curtis Malloy, a research specialist on epidemiology and infectious diseases, did not set out to “prove” or “disprove” the bible story. Rather, they were seeking a rational explanation, based upon what they knew about health and disease in modern-day human populations, for mysterious events that may have occurred in the distant past. That explanation, if it could be achieved, would neither confirm nor refute the central biblical theme of divine agency. For believers in the Old Testament record, it would merely demonstrate the mechanism through which God’s will was done. For non-believers, it would show how events described in the bible might relate to actual “plagues” or catastrophes in the ancient world around that time.

Egypt was experiencing the classic symptoms of a sudden imbalance in a delicate eco-system triggering off a series of interrelated surges and collapses in the populations of different species. The din flagellate (algae) bloom killed off the fish; the death of the fish produced a huge increase in the frog and toad population; this was followed by a population collapse, which in turn led to an upsurge in the insect population, which was free to breed unhindered in the absence of an important natural constraint.

1st Plague – The most common scientific explanation for such a phenomenon has been that it was a product of algae or silt in the river. It has been suggested that volcanoes in Ethiopia — which would have been active in biblical times — deposited huge quantities of sulphurous lava and ash into the river, turning its waters red, and making them undrinkable and killing the fish.

In the spring of 1997 millions of fish were dying in the waterways of North Carolina, their flesh afflicted by deep, open sores. Reports told of the rivers of the region turning red as the disaster unfolded. So-called “red tides” brought on by algal blooms in seawater are relatively well known; the algae responsible contain red pigment, which accounts for the water changing colour.  If an algae called Pfiesteria, or a similar freshwater din flagellate, had bloomed in the waterways of ancientEgypt, the combination of the blood from the dying fish and the red pigment that occurs in some strains of the organism, would account for theNileturning red. And the water, like that in North Carolina, would have become so toxic as to be undrinkable.

On April 14,1998 the waters aroundHong Konghave succumbed to a scourge known as the red tide, which is gobbling up marine life. This lethal build-up of toxic microscopic organisms has occurred before but never with the vengeance with which it has hitHong Kongin recent weeks. Sham Cun-hung, assistant director of agriculture and fisheries, said yesterday that it had wiped out 150,000 tons of fish, half ofHong Kong’s fish stock, in just four weeks.

A number of other examples have occurred recently in the Mediterraneanand other seas and river estuaries throughout the world. Caused by algae that soak up oxygen and release fish-killing toxins, they are usually short-lived, appearing suddenly in warm, still water but subsiding within two or three days.

2nd Plague -A mass death of fish would have freed the frogs’ spawn from its most important predator, so that unusually large numbers of frogs would have developed into maturity. In turn, these would have been forced away from the toxic waters of theNile, migrating in great numbers to the land, where they would have died and decomposed

Tsefardea”, the word used in the bible to describe the second plague, is a catchall description for all kinds of frogs and toads. It is believed that the behavior of the “tsefardea” as described in the bible best fitted that of toads — and toads of the genus Bufo, in particular.  They produce huge numbers of eggs — hundreds of thousands from a single individual. This means that populations of Bufo toads can soar from being relatively rare to numbering many millions. Bufo toads are also drawn towards sources of light and warmth in search of the insects that they rely on for food. The biblical description of how the tsefardea “came upon thelandofEgypt”, into the houses and bedchambers, the ovens and kneedingtroughs, fits the behavior of the Bufo toad perfectly. Marr and Malloy were convinced that this was the most likely candidate for the second plague, which came about as a direct consequence of the first.

3rd Plague – The original Hebraic word for “lice” (chinnim), as used in the bible to describe the third plague, could refer to any one of about 100 species of insect alive at the time inEgypt. It could also cover arachnids such as spiders, scorpions, ticks and mites. It almost certainly did not mean lice, as we understand the term today, however. For a start, the bible referred to them as afflicting both men and beasts, whereas the only lice we know of that afflict human beings do not afflict other animals. Scabies mite, Ticks or maggots, Black flies, Mosquitoes, have been ruled out.

Midges – (also known as gnats or, in US slang, “no-see-ums”) and sand flies. These tiny flying creatures are bloodsucking flies that fulfill the requirements for the use of the term chinnim. Eight species of midges (Culicoides) and seven species of sand flies (Phlebotomus) have been catalogued inEgypt. Midge larvae, moreover, feed on micro-organisms in decaying organic material (such as dead fish or frogs), and their emergence in huge numbers might indeed be seen as a plague arising from the dust of the land. Increasingly, however, they have been associated with both human and animal viral diseases. When Marr and Malloy came to research the fifth plague in detail, they came upon evidence that the biting midge was responsible — confirming them in their judgment that it was the creature referred to in the biblical account of the third plague.

4th Plague.  It is hardly surprising that the putrefaction of the river Nile and the mass deaths of fish and amphibians, during that time of the year when theNile’s flood waters would have been receding anyway and leaving behind pools of stagnant water, should be followed by plagues of “lice” and flies. The question was what kind of fly did the biblical account of the fourth plague refer to? John Marr contacted his old professor at the Harvard School of Public Health, the leading entomologist, Andrew Spielman, to narrow down the many possibilities into a shortlist. The horse fly, the housefly, the black fly, the stable fly, and Tsetse fly were ruled out.  The most probable candidate for the fourth plague seemed to be the stable fly.

5th Plague.  There have been six principal candidate diseases disease affecting animals but not human beings that were ruled out, Anthrax A, malaria, Surra A protozoan disease, Rift Valley fever A viral disease, Rinderpest and Foot-and-Mouth disease.

African Horse Sickness is a viral disease that affects horses, mules and asses, multiplying in the cells that line blood vessels, allowing blood fluids to get into the lungs and causing the animals literally to drown in their own fluids within a matter of hours.  Bluetongue is a virus, which affects cattle, sheep and goats in a similar way.

He also offered an explanation why two such viruses might have been spread so quickly at the same time in ancientEgypt. Both viruses are spread by the Culicoides midge, which Marr and Malloy had already identified as the most likely candidate for the third plague — of lice. This also offered a possible explanation why animals belonging to the Israelites could have been spared the fifth plague. Culicoides are very weak fliers, and herds and flocks outside their normal distribution range (such as in theLandofGoshen, where the Israelites resided, in northernEgypt) would have been spared their depredations.

6th Plague -.  Unlike the fifth plague, the sixth — of boils and blains — affected both animals and human beings. Previous scientific explanations have included anthrax and a combined staphylococcal/streptococcal bacterial infection. However, the variety of different ticks required to carry this disease to different species makes this unlikely.

Marr and Malloy proposed a new possibility: Pseudomonas mallei, the bacterium responsible for glanders, a highly contagious infection, which can be spread in the air, by direct contact or through fly bites. Used as a biological warfare agent in the First World War and first described by Aristotle in 330 BC, it is known as the “forgotten disease”. But in fact it is still found today throughout the Middle East andAfrica, affecting both animals and human beings. It spreads via the lymphatic system, causing the lymph nodes to swell and suppurate — hence the name, glanders — and fits the description of a plague of boils and blains extremely well. Its most likely carrier would have been the stable fly

7th Plague -Hail can occur almost anywhere in the world, although storms of such ferocity tend to be associated with hotter regions. The hailstones are ice balls created by updrafts of air, which carry water droplets to the top of storm clouds, where they freeze and then fall back down towards earth. They may then be carried upwards again in a succession of updrafts, collecting further water droplets en route and growing in volume each time that they do so. The diameter of the hailstones may range from one or two millimeters to 13 or more centimeters. Even the smallest stones can cause great damage to crops and vegetation; showers of the larger ones can kill or seriously injure animals or human beings caught out in the open.

One such violent hailstorm took place inIsraelandJordanin October 1997. Some 60 people were injured, buildings and vehicles were damaged, and the hail lay more than a meter deep on the ground. In ancientEgypt, a storm of this kind would have caused severe damage to the mud brick buildings of the Egyptian peasantry, as well as injuring or killing people and livestock who were unable to take shelter. Most devastating of all, it would also have resulted in immense damage to the growing crops at a time when, because of the previous plagues, this agrarian society was even more dependent upon the success of its harvest than usual.

8th Plague.  Marr and Malloy pointed out that for the ancient Egyptians, a plague of locusts — coming so soon after the plague of hail, which would have caused great damage to crops and fruit trees already — would have resulted in a desperate urgency to save whatever they could of their diminished harvest. Partially damaged crops would have been hastily carried to sheltered granaries and underground storage facilities. These crops would have been dampened and damaged by hail, with no time to dry or sort them before storing. They would also have been contaminated by locust feces, rich in bacterial and fungal organisms, all of which would have significant implications for the tenth and final plague

9th Plague.  Some analysts have suggested that the darkness was an accompanying feature of the plague of locusts; and certainly modern-day swarms of locusts can be so dense as to farm dark clouds as they fly and plunge the areas onto which they descend into an intense gloom

A khamsin, is a hot southerly wind sweeping in from theSahara. This wind can produce fierce sandstorms during the khamsin-season (from March to May). Typically lasting for two or three days, such as one that struckCairoin the spring of 1997. These storms have been known to bury entire buildings and large monuments in fine sand, blotting out the sun in a dark, dusty haze. The massive sand drifts that can accumulate in the lee of buildings in such storms would have blocked entrances, preventing the inhabitants from entering or leaving until the storm subsided, as described in the biblical account. Past storms of this nature are one of the reasons for the preservation of ancient tombs and other monuments that in some cases have remained buried for several thousand years inEgyptbefore their discovery by modern archaeologists.

The likelihood that the plague of darkness was the product of a khamsin sandstorm was given added weight by the fact that the biblical timetable required the ninth plague to have taken place in March. Marr and Malloy noted that the first of the khamsin storms each year, taking place around this time, would also have been the worst, picking up all the accumulated fine sand from the previous year.

10th Plague.  Marr and Malloy turned again to their view of the ten plagues as an interrelated, causative process. What, among the cumulative consequences of the preceding nine plagues, might have led to the tenth?  Curtis Malloy hit upon what the two scientists hoped might prove the key to explaining the tenth plague — the locusts’ feces, which would have contaminated what remained of the Egyptians’ crops as they rushed to save what they could.

What organisms might the locusts have introduced that would thrive in the damp, fetid conditions of the Egyptians’ stores? The answer was mycotoxins.  Mycotoxins are chemical compounds produced by fungi while growing on organic substances, such as corn and other crops. The fungi themselves are not harmful, but the mycotoxins they produce as by-products can be extremely so.

It is thought that this airborne poison enters the bloodstream of its victims through the lungs, where it causes capillary bleeding. The mycotoxin released by the mould, although known to cause disease in animals, had not been associated with human ailments before. But since its identification it has been linked to a number of other mysterious human illnesses in places where the same sort of conditions — damp, decaying buildings in poor, often inner-city areas.

What might explain the differential impact on the firstborn?  There is a strong ancient tradition, mentioned in the bible, whereby the firstborn should not just be fed first but receive double rations of what food is available. Similarly, the first animals to feed would be the most dominant ones — typically the eldest. Mycotoxin poisoning could have occurred by breathing in the unventilated air from the grain stores or by eating the food prepared with the contaminated grain. Symptoms of the poisoning would have been quickly noticeable, which might have alerted other people to the dangers from the contaminated grain. In addition, deeper stores of grain and foodstuffs may not have been so affected by the surface-growing mould, sparing humans and animals that fed off it later. The grain stores themselves, moreover, would have been ventilated by this stage, removing the threat of exposure to airborne toxins.

The Israelites could have escaped the worst effects of mycotoxin poisoning, firstly, because theLandofGoshen, where they lived, escaped some of the earlier plagues that exacerbated the food shortages and famine in the rest ofEgypt. And secondly, it may be that the tradition of the Passover meal, in common with other dietary injunctions found in the bible, bears some relation to ancient understanding of food hygiene and safety. The key elements of that meal — newborn lamb, herbs and unleavened bread — are all safe from mycotoxin contamination. Is it possible that this was a means of reinforcing by religious myth some basic principles of good dietary practice?

The bible also contains detailed injunctions on how to deal with the presence of certain kinds of mould in dwellings. And a recently decoded fragment from the Dead Sea Scrolls, Cryptic B, apparently passed down from Moses’ teachings, contains an instruction for Jews to destroy any dwelling in which mildew was found. The ancient peoples of biblical times would not have know what mycotoxins were — but was it possible that they knew of their effects, and as part of their religious practices counseled methods of avoiding them?