Bulletin 5 - July 1978: Unwelcome Creatures of Abu Dhabi

Unwelcome Creatures of Abu Dhabi

Rats are undoubtedly the world's worst pests. There are 500 species of rodents but Rattus norvegicus (sewer rat) and Rattus rattus (ship rat) are the most common. However, I only saw one ship rat in Kuwait over a nine-year period, and I have seen none in Abu Dhabi. These rats are called commensal rats because of their habit of sharing the food from our tables. In the appalling living conditions of many third world countries this is quite literally true.

Rats breed fast. The average female produces six litters a year and ten young per litter. The Norway rat weighs about 500 gm., the ship rat less than half of this.

Rats transmit many serious diseases including leptospirosis and rat-bite fever. With the rapid growth of urbanization and the general disregard of the danger of human health caused by rats and the parasites they carry, WHO has warned that the world is confronted with the continuing menace of human plague. This is of particular significance to Arabian Gulf countries because of their proximity to plague foci.

Rats have sharp incisors in both upper and lower jaws which are set well forward allowing them to gnaw through hard and toxic materials with comparative ease, causing great damage to property and foodstuffs. In South-East Asia, for example, 33 million tons of food are lost annually because of rats. It has been calculated that a single rat left to roam freely in a warehouse for a year will eat about 2000 lbs of food, deposit 25,000 droppings and contaminate sacks, boxes and other items with urine.

Most of the diseases caused by rats can also be carried by mice and they cause a great deal of damage to food and all kinds of materials. They nibble constantly, feeding 20- 30 times daily and are able to survive with very little water. A typical litter consists of 6-8 young and the mother is capable of breeding again about a month later. The normal life-span of a wild mouse is less than one year and it rarely weighs more than an ounce.

The House mouse, Mus Muscullus, is even more widely spread than the two commensal rats and are hardly dependent at all on man. They rest in wall crevices, under floors, in roof linings, in outdoor burrows and in foodstuffs. They are extremely difficult to find and even more difficult to control. Heavy infestation by mice leads to a distinctive and unpleasant odor.

Flies were the fourth of the ancient plagues of Egypt and two-winged flies of the order Diptera remain of major medical importance to this day.

The common house fly, Musca domestica, is found everywhere in the world, spreading diseases such as cholera, dysentery, typhoid and trachoma. They breed in any moist. fermenting or putrifying matter, which is of particular importance in hot countries.

It is not surprising that visitors succumb to diarrhoea and there is a whole list of such afflictions from Abu Dhabi cramp to Malta Dog, Basrah belly, Rangoon runs, Ho Cho Mins, Tokyo Trots, Aztec Two-Step and Maladie de Zaire.

Flies are also extremely irritating creatures. They survive about a month in summer but seek shelter and warmth in colder weather. They have many natural enemies including certain ants, bacteria and fungi.

As well as house flies, there is a considerable range of blow flies and flesh flies which are attracted to fresh or decaying organic matter. In Abu Dhabi I have seen Caliphora, Lucilia, and Sarcophaga carnaria which is a large fly of 22 mm. wing span, grey-white in color with a striped thorax and checkered abdomen.

Sometimes called gnats, mosquitoes are delicate creatures which nevertheless are responsible for some of the worst vector-borne diseases in the world such as malaria, filariasis, yellow fever and dengue.

In spite of huge anti-malaria campaigns at least 100 million cases occur annually. There is no malaria in Abu Dhabi but Anopheles d'tali was recorded in 1970 in Wadi Sidi between Dubai and Khor Fakkan.

In the area as a whole An. stephensi and possibly An. fluviatalis are likely to be the most important vectors. Mosquito bites cause great discomfort. It is the proboscis of the female insect that pierces the skin to draw blood.

After mating the female mosquitoes lay eggs on the surface of water and a few days later they hatch and the larvae moult four times within a period of 4-10 days. The pupal stage lasts from one day to several weeks depending on the species. When they are ready to hatch the pupae work their way out of the skin which is used to support the body wall until it is ready for flight. The males emerge first and are capable of mating at the first opportunity with an emerging female.

These blood-sucking pests are common in Abu Dhabi. They are usually found in servants' quarters and labor lines but I know of one 1 case in an Embassy. In the absence of human blood they will feed on the blood of rats, dogs, mice, poultry and even canaries. Armed with a vicious "stiletto" they puncture the skin, lacerate the wound and absorb a blood-meal in 5-10 minutes. Bed bugs inhabit cracks and crevices in walls, wooden and steel bedsteads, loose wallpaper and the seams and buttons of mattresses.

During the carboniferous period two hundred million years ago cockroaches were present in enormous numbers, some being several inches long. They are great survivors: 3,500 species exist today mostly in tropical and subtropical countries. They like a warm humid environment and thrive in house and flat environments. They will eat a great variety of matter, including glue, organic remains, leather and hair.

Although cockroaches are not transmitters of specific diseases, they live in drains and sewers, coming out at night to feed. There is a considerable body of evidence to suggest that they carry germs both outside and inside their bodies.

The most common cockroach in Abu Dhabi is the American cockroach Periphaneta americana, so called because of its wandering nature. The German cockroach, Blattella germanica, is found in catering establishments in considerable numbers and I have encountered two gross infestations in private flats in Abu Dhabi.

Recently I was told that the Oriental cockroach Blatta orientalis had been seen in Kuwait. I was very skeptical, not having seen one in over nine years there, but a few weeks ago I found one in the Military Hospital in Abu Dhabi.

The Brown-banded cockroach, Suppella supellectilium, was reported from Dubai some years ago.

Cockroaches go through the usual stages of eggs, larvae and adluthood. The eggs are carried in purse-shaped cases called ootheca, with two rows of eggs on each side. The American and oriental species have 8 eggs on each side, while the German cockroach has 12-14.

Nymphs of the oriental cockroach take 10 months to 2 years to mature, the American about 18 months and the German less than 9. Cockroaches usually walk but are capable of short flights. The cockroaches of Abu Dhabi are insignificant compared to the lobster cockroach, Nauphoetea cinerea, which reaches a length of 11/4 inches and carries 26-40 eggs. It is mainly found in Florida.

Ants live in colonies in the ground and are social insects with a well-developed caste system. The colony is started by a newly-mated queen which drops her wings and immediately seeks a place of safety to start the nest. The queen seals herself in and remains dormant while the eggs develop in her body. All being well the colony expands rapidly with numerous males and additional queens being formed.

There are at least four species of ants in Abu Dhabi which in decreasing order of size are:

and a very small, so far unidentified, species of brown ants.

Within a broad band encircling the tropics and subtropics termites cause immense damage. Like ants they are social insects with highly specialized tasks. There are some 1,700 species divided into two main groups, subterranean termites and dry-wood termites. They live in nests underground or in mounds or hillocks above ground level.

Termites cause very little damage in the arid parts of the Middle East but they are present in Kuwait (Ahmadi and Kuwait City), and have been recorded in Al Ain.