Problems and prospects associated with integrated methods of rodents’ control

Introduction

Worldwide, rodents have been, and continue to be, a major vertebrate pest group that has been a major concern to man and its environment. Much effort has been, and continues to be, expended to reduce their numbers and damage (Witmer, Fall & Fiedler, 2005). Rodents are known to have been involved in many types of damages, including damages to crops, trees, structural property, destruction of industrial raw materials and finished goods, and transmission of disease to man (Witmer et al., 2005).

Numerous books have appeared in the last decade from all continents or regions of the world, addressing rodent damage and its management (Corrigan, 2011).At the same time, rodents have many important ecological roles and most species are not major pests. Some of the roles include soil mixing and aeration, seed and spore dispersal, influences on plant species composition and abundance, and a prey base for many predatory mammals and birds, acting to sustain populations of these species. However, rodents also are important vectors or reservoirs of numerous diseases that infect humans, domestic animals, and other wildlife species. They are significant economic pests that devastate crops, gardens, orchards, or landscape plantings, and damage commercial forest plantations or impede reforestation efforts (Desoky, 2007).

Corrigan (2011) pointed out that rodents burrow through dams and irrigation structures, gnaw through communications cables and damage electronics, and consume or contaminate stored food and other commodities. Depending on the species of rodents involved, the kinds of environments where problems occur, the nature of the problem, and the value of anticipated damage, a variety of methods is available for controlling damage or reducing rodent populations. Usually, several methods need to be used systematically to achieve lasting results. The process of selecting, applying, and evaluating the results of such combinations of control methods in relation to the ecological and economic aspects of specific damage problems is called integrated pest management (IPM) or ecologically-based pest management (Allen, Lee & Rance, 2009).

Conceptual framework

According to Mulugu, Makindi and Massawe (2006), the most successful and abundant mammals on earth apart from man are rats and mice. They stressed that man is an adaptive animal, but sometimes his adaptive mechanism waits there by exposing him to migrate to condition that endanger his health and well-being. Apart from contending with these animals that compete with man for food and dominance, he is exposed to the activities of micro-organism, disease vector and pests.

Liere (2008) states that rat and mice are parts of man’s environment and their number exceed human population. A female rat can have 100 offspring each year by living in close proximity to man, they did not only cause substantial economic loss by damaging building, consuming and contaminating food stuff and other commodities but also act as sources of reservoir of some important communicable diseases such as plaque and typhus fever. It implies therefore that destruction of rats and elimination of their habitats is an important measure.

Origin of rodents/classification

Higley and Pedigo (2009) stressed that rodents co-habit with man, i.e. wherever man is found, rodent is usually found there. They compete with man for food and in the process they destroy large quantity of food stuffs, property and also spread disease to man. Rodents are found at improperly and insanitary managed waste disposal sites. Rodents are omnivorous, i.e. they eat all kinds of food consumed by man and by nature rodents give birth to a large number of young ones. Walker (2010) also noted that a premise is said to be rodent infested when the premise harbour a large proportion of rats. Some signs showing the existence of rodents in a premises or environment according to Norrdahi (2005) include:

1. Presence of rats’ burrows
2. Presence of runways or run
3. Dead rats in the premise
4. Sighting of rat droppings
5. By hearing their sound when running and scratching the wall and gnawing for food.
6. Another important method of knowing that rodent is present in a house is by suddenly putting on light at night. It this way, rodent will either be sighted or their noise will be heard as a result of their running for safety.

Mode of spread of rodents

Kerbs (2006) stated that generally rat can travel from one place to another especially pursuing object of attraction, like food. This movement is said to be very important in the community especially to the bakery as it aids the transmission of plaque and other diseases. Rats can move from the nearby bush into a bakery. In fact the prevalence of plaque is due to part of the seasonal movement of rats.

Rats like other animals prefer to remain in a limited area called home range for long period of time. The number of young ones produced depends on the environment and the general situation of the area and capacity to support rats’ population. Rodents and mice nurse their young ones in litres and the number of the young one in litters, and the number of the young ones in a litter varies with the species. It is about nine (9) for sewer rats, six (6) for roof rats and three (3) house mouse. The average number of litter per year is about four (4) for sewer rats, five (5) for roof rats and six (6) for house mouse respectively. Rattus and rattus and rattus norwegian breed often producing 0 – 4 litres (young ones) after a gestation period of 3 – 4 month and can live for 2 – 5 years. They can breed throughout the year despite variation in seasons (Lurz, 2010).

Characteristic of rodents

Rodent is a member of the mammalian order rodent, characterized by front teeth adapted for gnawing and cheek teeth adapted   for chewing. The rodent is by far the largest mammalian order, nearly half of all mammalian species are rodents. They are worldwide in distribution and are found in almost every terrestrial and freshwater habitat from the shores of the Arctic Ocean to the hottest deserts.

They are variously adapted for running, jumping, climbing, burrowing, swimming and gliding. Many of them have dexterous fore-paws which they use as hands while sitting on their hunches in a position characteristic of many rodents. The great majority are under a few inches in height, the largest the capybara is about 4 ft (120cm) long and 20in (50cm) high at the shoulder.

Mode of transmission of rodent borne diseases

Myllymake (2007) stated that rodent infestation is always considered dangerous because, they can carry diseases; rats often inhabit sewers and can transmit disease to man who work where there is spirochete which causes a serious form of jaundice. Walker (2010) further noted some diseases associated with rodents as observed by the World Health Organisation [WHO] (2010) to include plaque, lassa fever, marine typhus, leptospirosis, rat bit fever, salmonellosis, trichinosis, tularaemia, etc.

Mulungu et al., (2006) stated that rats are connected with the spread of plaque and other infectious diseases, therefore strict regulations should be enforced to reduce their population. In this regards, every ship from foreign port must hold a valid derating exemption certificate and this certificate is issued, but if rats are present, the ship is fumigated and derating certificate is issued.

The regulation further stressed that there are many types of rats, but only two are strongly connected with plaque. These are rattus rattus and rattus norvigicules. Rat should be prevented from coming into contact with man especially in ports as people cross and recross political boundaries. Lurz (2010) stated that rodents are reservoir of infections for many diseases. These diseases are spread either through rat bites or man eating food that has been contaminated by rats. Fleas wound also inflicted on people which rat and mice bite when sleeping.

Damages caused by rodents’ activities

Mulungu et al. (2006) state that the most successful and abundant mammal on the earth surface apart from man are rats and mice. These animals live at the expense of man, they compete with man for food and in the process destroy large quantity of food stuff, properties and also spread diseases to man. They also inhabit abandoned premises, construction sites, abandoned automobiles, undeveloped plots of land, drawers, stores, regulated premises, etc. Rats cause damages to our farm products, food stock in the house and damage our properties. The major source of food for rodents is garbage, store food, bread, crops, grains, etc. They also eat food such as meat, vegetables, fish and fruits.

According to Norrdahl (2005), the major pest species of rodents are:

• Brown or Norwegian rat (rattus norvegious)
• Roof, ship or house rat (rattus rattus)

Some symptoms of rats and mice attack on crops as stated by Norrdahl (2005) include:

• Holes are made in nuts aged between 3 – 6 months, e.g. coconuts.
•  Rats dig up and consume seed and seedlings of maize.

Prevention and control of rodents/ rodent-borne diseases

The economic losses resulting from rats and mice infestation are unquestionable and the numbers of deaths due to rodent-borne diseases are innumerable, therefore there is urgent need for it to be controlled. The focus of all rodent control programmes is to reduce their population and eliminate them from human habitation. These can be achieved through a number of ways.

Nicholas and Hines (2007) pointed out some of the ways by which good management of rodent could be achieved with the aim of attaining a high degree of physical, mental and social well-being of workers. The following prevention and control measures are discussed as follows:

1. Rat guards: This is a circular usually used in vessels. Sheet metal shield mostly used in a vessel to control rodent by preventing them from boarding or leaving it.
2. Environmental sanitation: This generally include all those measures that are chemically less or predictive. It include keeping of houses in good sanitary condition. It deprives rat/mice from sources of food harbour in the area. This can be achieved through maintenance of drains, wrapping garbage and storing in a rust roof dust with a tight fitting cover. Storing of food stuff 12 – 18 inches off the floor in a closed container, proper disposal of waste, storing of items in a manner that will not provide harbourage of rodent/mice, keeping animal feeds cleaned up and regular cutting of bushes around homes, offices, schools and market place.
3. Rat proofing: Rat proofing is the eliminating of all holes to prevent rats from entering residential building and food establishment. A building can be rat proofed, eliminating all openings larger than ½ inch. For rat and ¼ for mice. All doors, windows that do not operate properly or shut securely should be repaired, repair air vents that may not be in sound working order, broken glasses or stones and get them properly cemented.
4. Trapping: Another method of controlling rodents is by the use of traps to kill them. Wooden or metal or rat book type of trap are the commonly used in these connection. For success to be achieved, large number of traps must be used at a time. Rats usually avoid source of death if the trap is in one corner of the house. They will it at another site and many of them would be killed in the process, traps must be placed against the well behind bags of flour and already baked bread. Always use new bait daily and trap must be disinfected after each use. If this is not done, the smell of the trap will scare the rodents away.
5. Fumigation: The control of rodents by fumigation can be very effective by the use of chemicals, but may be expensive and dangerous. Fumigation is a process of eliminating rodents of public health importance in the ship, store, warehouses, factories or regulated premises, homes by the use of chemical fumigants. Before fumigation is carried out, the fumigator must know the choice of chemical to be used as some of them are more dangerous and harmful to the health of users and some of them have been banned or severely restricted because of evidence harmful effects on human being and the fumigator must know the following.

• The type of infestation, infection and the object of infection.
• Must know the effective agent.
• Must know the rate of infection and the area coverage.
• The concentration of the chemicals.

References

Allen, R.B., Lee, W.G. & Rance, B.D. (2009). Regeneration in indigenous forest after eradication of Norway rats, Breaksea Island, New Zealand. New Zealand Journal of Botany 32:429-439.

Buckle, A. P. & Smith, R.H. (2009). Rodent pests and their control. Wallingford: CAB International

Corrigan, R. M (2011). Rodent Control. Cleveland: GIE Media.

Desoky, A. S. (2007). Management strategies for rodents within different ecosystems. M. Sc. Thesis, Fac. Agric. Assiut Univ. New York.

Fiedler, L.A. & Fall, M.W. (2010). Rodent control in practice: tropical field crops. Wallingford; CAB International.

Higley, M. & Pedigo, L. (2009) Observations on an exceptionally dense population of wild rats in marshland. Kalikasan (Philippine J. Biol.) 5:207-212.

Kerbs, U. (2006). Rodent problems in Asia. Florida: CRC Press.

Liere, C. (2008). Rats and mice, Cleveland: Franzak and Foster.

Lurz, D. J. (2010). Rodent and bird problems in agriculture and their management in developing countries. Proc. 11th International Congress of Plant Protection 11 (Vol. I): 65-73. Manila, Philippines.

Mulungu, B. Makindi, Y & Massawe, K (2006), Immunocontraception as a wildlife management tool: some perspectives. Wildlife Society Bulletin 26:237-243.

Myllymake, A.  (2007) A program for control of damage by the field vole, Microtus agrestis (L.), in seed orchards of forest trees. EPPO (European Plant Protection Organization) Bulletin 7:523-531.

Nicholas, V. & Hines. O. (2007). Biological control of vertebrate pests. Proceedings of the Vertebrate Pest Conference, University of California, Leaflet 28:96-101.

Norrdahi, M. H. (2005). Preliminary assessment of small wild mammal populations in tall fescue habitats. Tennessee Farm and Home Sciences 160:68-71.

Walker, H. (2010). IPM strategies: indexing difficult to monitor populations of pest species. Proceedings of the Vertebrate Pest Conference 19:183-189.

WHO (2010). Control of leishmaniases. WHO Technical Report Series No. 793, 158p.

Witmer, G., Fall, M.W.  & Fiedler, L. A.  (2005). Rodent control, research, and technology transfer: Integrating people and wildlife for a sustainable future. Proceedings of the First International Wildlife Management Congress. The Wildlife Society, Bethesda, MD, USA.