This article is from
Creation 31(3):34–37, June 2009

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What about parasites?


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If God created everything ‘very good’, why are there harmful parasites?

When I worked as a doctor in a bush hospital in Tanzania, East Africa, I treated many patients for a disease called Bilharzia, or Schistosomiasis. This is a parasitic disease caused by several species of fluke, or flatworm, of the genus Schistosoma. The particular form of the disease which I treated was the one caused by the species Schistosoma haematobium.1

This worm, like so many other parasites, has a bizarre and complex life-cycle which defies an evolutionary explanation.

It assumes seven different forms as it progresses through its life-cycle, and part of that cycle takes place within an intermediate host, a freshwater snail. The complexity of such organisms points to a Creator; but the existence of disease-causing parasites and microbes does also raise questions concerning God’s “very good” creation and the global Flood of Noah’s day.

Evidence for creation

As far as their physical structure is concerned, all living creatures—including the most basic and ‘simple’ forms of life (one-celled organisms)—are stupendously complex, sophisticated, computerized machines. Molecular biologist Michael Denton has estimated that if we knew how to build a machine as complex as the cell, it would take at least one million years to build one cell—working day and night, and churning out the parts on a mass production basis.2

One kind of complexity is the way in which some animals exist in several completely different forms during their life-cycles. The butterfly, for example, exists as an egg, a caterpillar, a chrysalis and a butterfly. Within the chrysalis, the internal organs of the caterpillar dissolve into a soup, and then this soup organizes itself into a beautiful, incredibly complex, adult butterfly! The whole process, from egg to butterfly, is coded in the genes, and is a marvel which defies any kind of evolutionary explanation.3

Degeneration in the human immune system could have contributed to our susceptibility to parasitism by formerly benign organisms.

The humble Schistosoma may not excite our admiration in the same way; but during its life-cycle it exists in seven different forms (including the egg)! Again, it is a marvel which defies an evolutionary explanation.

A God of love?

Schistosoma parasites, like every other living creature, are evidence for creation; but they also raise certain questions. Sir David Attenborough has often been asked why he does not give the credit to God when he describes the wonders of creation. This was his reply on one occasion:

“When Creationists talk about God creating every individual species as a separate act, they always instance hummingbirds, or orchids, sunflowers and beautiful things.

“But I tend to think instead of a parasitic worm that is boring through the eye of a boy sitting on the bank of a river in West Africa, [a worm] that’s going to make him blind.

“And [I ask them], ‘Are you telling me that the God you believe in, who you also say is an all-merciful God, who cares for each one of us individually, are you saying that God created this worm that can live in no other way than in an innocent child’s eyeball? Because that doesn’t seem to me to coincide with a God who’s full of mercy.’”4

Notice that Attenborough did not give a scientific reason for rejecting belief in a Creator. He gave a theological reason for rejecting belief in the good and loving God of the Bible. The first question, therefore, is “Why did God, if He is good and loving, create disease-causing parasites—not to mention all the other disease, violence, suffering and death which we see around us in nature?”

The straightforward, biblical answer is that these evils did not exist in the original creation. They came into the world only after the Fall, when Adam and Eve disobeyed God (Genesis 3:14–24; Romans 8:18–25). They were part of the “Curse” (Revelation 22:3). Six times we are told that God saw that His creation was “good”, and the seventh time He saw that it was “very good” (Genesis 1:4–31).

Seven is the “perfect number”, and the sevenfold repetition of the phrase “it was good / very good” signifies the absolute goodness and perfection of the original creation. The presence of any kind of evil, moral or physical, is absolutely denied. Disease is clearly a physical evil. It was not present in the original creation, and it will not be present in the new creation either, when God creates a new heaven and a new earth (Isaiah 11:6–9; Isaiah 65:17-25; Acts 3:21; Romans 8:18–25; 2 Peter 3:1–13; Revelation 21:1–5; Revelation 22:3).

Theistic evolutionists and other Christians who accept the secular belief in “millions of years” cannot give this answer. They believe that God’s method of creation was a process of millions of years of death, disease, violence, suffering and waste.

The fossils (which they believe represent millions of years of life and death on earth before the Fall) show clear evidence of all these evils. For example, some of the fossils show evidence of cancer. Can cancer be described as “very good”? It is hardly surprising that many non-Christians say that such a god (if he were to exist) would be cruel or incompetent, and would be unworthy of their worship.

The origin of harmful parasites

The second question is this: If disease-causing parasites did not exist in the original creation, how did they come to be here now? We do not know the answer for certain, but we can reasonably speculate. I think it is unlikely that they were specially created after the Fall, as Genesis 2:1–3 says that God finished his work of creation “by the seventh day” (cf. Exodus 20:11).

If that is correct, these parasites must have been benign and beneficial in their original form. Perhaps some were independent and free-living, and others had beneficial symbiotic relationships with animals or humans. But when Adam and Eve sinned, things began to go wrong. These once-harmless creatures degenerated, and became parasitic and harmful. The Fall and subsequent Curse were unique events which took place soon after the beginning of human history. So there is no compelling reason why God should not have caused these organisms to become pathogenic (disease-causing) miraculously. However, there are other methods He could have used.

Perhaps some became parasitic as a result of mutations. They degenerated, lost their ability to live independently or symbiotically, and became harmfully dependent on their hosts. Note that mutations overwhelmingly cause loss of genetic information. Such degenerative changes are evident in disease-causing microbes like a Mycoplasma that causes a type of pneumonia and the germs that cause leprosy and cholera.5

Parasites must have been benign and beneficial in their original form.

Other kinds of genetic change may have been involved too. For example, microbes can swap genes. The bacterium that causes bubonic plague probably resulted from more than one kind of change.6

In many cases, however, the life-cycle of the parasite is so complex that new genetic information may have been needed. Mutations do not provide new genetic information; so the information may have been there from the beginning. However, it was in a ‘switched off’ mode before the Fall, and was not ‘switched on’ until after the Fall. God could have included this genetic information because of his foreknowledge that Adam and Eve would disobey him.

Another possibility is that some parasites had symbiotic relationships with animals, and they became parasitic and harmful only when they invaded humans. Also, degeneration in the human immune system could have contributed to our susceptibility to parasitism by formerly benign organisms.

These evils did not exist in the original creation

Parasites on the Ark

The third question is this: If the eight people on board the Ark were the only human survivors of the global Flood, how could they have carried all the disease-causing parasites and microbes which can survive only in humans? Biblical creationists are ridiculed about this, not only by non-Christians, but also by theistic evolutionists and other old-earth creationists, who believe that Noah’s Flood was local. Possible answers are not difficult to find, however, if one is prepared to look for them.

The most obvious answer is that most, if not all, present-day pathogenic organisms that can dwell only in humans did not exist in their present form at the time of the Flood. There has been plenty of time for them to develop since the Flood. Many pathogenic organisms which existed in the pre-Flood world may have perished in the Flood, but others have taken their place.

Wikipedia Skin vesicles on the forearm, created by the penetration of Schistosoma.
Skin vesicles on the forearm, created by the penetration of Schistosoma.

One suggestion is that some pathogens which can survive only in humans today were much less specialized at the time of the Flood.7 At that time they were able to flourish in a wide variety of animals; but since then, they have become entirely dependent on human hosts. Common viral diseases of humans today may well have derived from animal diseases. A New Scientist report states:

“Just as historians such as William McNeill, of the University of Chicago, and other researchers trace smallpox back to cowpox, so measles probably evolved from rinderpest or canine distemper, and influenza from hog diseases.”8

Some of Dr Wieland’s suggestions7 involve organisms which were already pathogenic (usually in animals) when the Flood began. Asymptomatic carriers could have carried some diseases on the Ark. All the organisms which became pathogenic after the Fall, however, had to be derived from organisms which were entirely benign.


The Schistosoma parasite, like so many other pathogenic organisms, is a thoroughly unpleasant creature. It speaks to us of a creation which has been spoiled because of man’s rebellion against God. In spite of this, its complexity and remarkable life-cycle are a witness to the power and divinity of God (Romans 1:20).

The existence of such pathogenic organisms raise certain questions. To answer these questions, we could invoke miraculous intervention by God—and in fact it would have been quite reasonable for Him to intervene miraculously in the unique circumstances of the Fall and the Flood—but we do not have to do this. We just have to be willing to look for reasonable answers, and take the trouble to do so!

Technical information: Schistosomiasis life cycle


Skin vesicles on the forearm, created by the penetration of Schistosoma.

Life-cycle of Schistosoma haematobium
(Click for larger image)

The parasite begins life as an egg, which is shed into the ureter or the bladder of the human host. It is passed out of the body with the urine, and on contact with fresh water, it hatches to release a free-swimming “miracidium”. This is a ciliated organism, swimming by means of its many hair-like cilia. It finds a fresh-water snail and penetrates the snail’s foot. Here it transforms into a “primary sporocyst”. Germ cells within the primary sporocyst then begin to divide and produce “secondary sporocysts”. These migrate to the snail’s hepatopancreas. Germ cells within each secondary sporocyst then begin to divide again, this time producing thousands of new parasites, called “cercariae”, which emerge daily from the snail host. These have tails, and are highly mobile. They are the larvae capable of infecting humans. Penetration of the human skin occurs after the cercaria has attached to and explored the skin. The parasite secretes enzymes that break down the skin’s protein to enable penetration of the cercarial head through the skin. As it penetrates the skin, it loses its tail and transforms into the migrating “schistosomulum” stage.

The schistosomulum enters the blood stream and travels to the lungs, where it undergoes further developmental changes before migrating to the liver. In the liver, it begins to feed on red blood cells, and it is there that the nearly mature worms pair, the longer female residing in the ‘gynaecophoric channel’ of the shorter male. The adult worms are about 10 mm long. The worms ultimately migrate from the liver to the venous plexus of the bladder, ureters and kidneys. When the parasites reach maturity, they begin to produce eggs, and these pass through the ureteral or bladder wall into the urine.1

  1. For more information about schistosomiasis, see <en.wikipedia.org/wiki/Schistosomiasis>; <www.cdfound.to.it/html/gen1.htm>.
Posted on homepage: 6 September 2010

References and notes

  1. For more information about schistosomiasis, see Schistosomiasis and Schistosoma haematobium. Return to text.
  2. Denton, M., Evolution: A Theory in Crisis, Adler & Adler, Maryland, USA, pp. 329–330, 1985. See Sarfati, J., By Design, Creation Book Publishers, Brisbane, Australia, chapter 11, 2008. Return to text.
  3. Devine, D., Inexplicable insect metamorphosis, Creation 29(3):31–33, 2007; Return to text.
  4. Sir David Attenborough: so much to live for; nothing to die for!, 2008. Return to text.
  5. See Sarfati, J., By Design, chapter 13, Creation Book Publishers, 2008. Return to text.
  6. Gillen, A., and Sherwin, F., The origin of bubonic plague, Journal of Creation 20(1):7–8, 2006; Return to text.
  7. Wieland, C., Diseases on the Ark, Journal of Creation 8(1):16–18, 1994; <creation.com/diseases>. Return to text.
  8. Meltzer, D., How Columbus sickened the New World, New Scientist 136(1842):38–41, 10 October 1992. Return to text.