Vector Borne Diseases and Vector Control Vectors Vectors
Vector Borne Diseases and Vector Control
Vectors � Vectors are invertebrates or arthropods or animals which transmit disease either through ingestion, injection or contact.
Nuisance Pests: Cockroach A female German cockroach only needs to mate once. She can fertilize all the eggs she will produce in her 9 month lifespan and produce about 200 offspring
Rats and Fleas � There about 1600 species of fleas in the world A single adult pair of rats can produce 500 offspring in a year. A pair of breeding owls which produce five to six chicks in a year can eliminate up to 3, 000 rats in a year
Vector-borne Disease Burden � � � � The major burden of disease in the African region is attributable to vector borne diseases. These include malaria, lymphatic filariasis, trypanosomiasis, onchocerciasis, schistosomiasis, dracunculiasis, yellow fever and dengue fever. It is estimated that 90% of global clinical malaria cases (300 million) and malaria related deaths (1 million) annually occur in the continent. About 55 million people are at risk from trypanosomiasis. Although onchocerciasis is controlled in 11 West African countries, the disease is still a public health problem in 19 countries including Nigeria. Plague also remains a problem in at least 11 countries and outbreaks in Nigeria have recently been reported. Leishmaniasis is endemic mainly in East Africa where a sharp increase in the number of cases has been observed. There are 164 million people infected with schistosomiasis and 477 million people are at risk world wide. The incidence of Guinea worm has been dramatically reduced but substantial efforts are still needed in Nigeria and some countries.
Guineaworm Lifecycle
Guineaworm Countries
Guineaworm � � � Guinea worm enters the body when people drink water containing cyclops. infected with the guinea worm larvae. Cyclops die in the stomach and release the guinea worm larvae to move through tissue in the intestines. Male and female worms mate after about three months. The male worm dies. After about eight months, the mature female worm moves toward the surface of the skin (usually the lower limbs). After about one year from the time the person drank the infected water, the worm is ready to emerge from the body. The infected person has felt no effects up to this time. A painful blister forms. Infected people try to relieve the pain by immersing the sore in the water. Contact with water causes the guinea worm to emit its larvae, recontaminating the water source and perpetuating the cycle of the disease.
Schistosomes (also known as Blood fluke) are one of the major human helminth parasites endemic in 74 developing countries, threatening 650 million people and causing severe morbidity especially in children under the age of 14 (WHO, 2008). It is due to a trematode of the genus Schistosoma, of which 5 species are the principal causes of the human disease, i. e S. mansoni, S. haematobium, S. japonicum, S. mekongi and S. intercalatum.
Onchocerciasis
Trypanosomiasis Trap using pheromones
Factors to consider in vector control � Life history of vector: Most of the vectors are insects with complete or incomplete metamorphosis � Habits: knowledge of feeding, resting and flying habits � Cost of control � Ecological consideration: it helps to envisage how the plan of action will affect the totality of the environment. It is important that an Environmental Impact Assessment (EIA) of the planned action be carried out before proceeding.
Typical Stages in the Life Cycle of Mosquito
Malaria Anophelis gambiae A, funestus • Plasmodium falciparum occurs throughout tropical Africa and in parts of Asia, the Western Pacific, South and Central America, Haiti and the Dominican Republic; • Plasmodium vivax is almost absent from Africa but is the predominant malaria parasite in Asia and South and Central America; • Plasmodium malariae is found worldwide but has a very patchy distribution; • Plasmodium ovale occurs mainly in tropical West Africa and rarely in the Western Pacific.
Epidemiology of Malaria in Nigeria S/N ecological zone 1 states Transmission period (months) Strata definition Sahel Savannah Borno and Yobe 1 -3 Unstable/ epidemic prone An arabiensis 2 Sudan Savannah Adamawa, Bauchi, Gombe, , Katsina, Jigawa, Kebbi, Sokoto and Zamfara. 4 -6 Unstable/ epidemic prone An arabiensis 3 Guinea Savannah Kogi, FCT, Benue, , Taraba, , Nassarawa, 4 -6 Unstable/ epidemic prone An arabiensis 4 Forest Mosaic , Kwara, Anambra Ekiti, 4 -6 Unstable/ epidemic prone An arabiensis 5 Forest Lagos, Ogun, Osun, Oyo, Delta, Ebonyi, Edo, Imo and Abia. 7 -9 Unstable/ epidemic prone An arabiensis 6 Mangrove Cross River, Akwa Ibom, Rivers, Bayelsa 9 -12 Stable An gambiae & An funestus Ondo, Malaria vectors
National Vector Control Programmes � There are established programmes aimed at the control, eradication and or elimination of these vector borne diseases: - - Roll Back Malaria, - Nigerian Guinea worm Eradication Programme (NIGEP), - National Onchocerciasis Control Programme, - National Schistosomiasis control - Lymphatic filariasis elimination programme, - Trypanosomiasis eradication programme etc.
Mites, Ticks – Other Acari, Reduvid bug Mites and ticks which feed on vertebrate hair or blood often carry disease organisms, such as spirochete bacteria, responsible for relapsing fever and Lyme disease. � Others are rather unpleasant parasites themselves, such as ticks, chiggers, and the skin mites that cause mange and scabies. Yet most mites are free-living, found in great abundance in soils, plant litter, and even in water. � In all there about 30, 000 species of Acari known, and that is probably only a fraction of the actual number of species. �
Bugs and Lice
Vector Control Methods Environmental Control 2) Chemical Control 3) Biological Control 4) Genetic Control 1)
Environmental Control � Water control � Drainage clearing � Filling burrow pits and abandoned ditches, holes � Flushing � Drying of breeding places � Management of irrigation water � Removal of marginal and other vegetation � Removing shade where mosquitoes breed � Disposal of empty cans, discarded tyres
Source Reduction � � � It consists of elimination of larval habitats or rendering of such habitats unsuitable for larval development. Public education is an important component of source reduction. What you/your family can do to prevent mosquito proliferation. e. g. Household drainage clearance and larviciding using oil or other agents. Other forms of source reduction include open marsh water management, in which mosquito-producing areas on the marsh are connected by shallow ditches to deep water habitats to allow drainage or fish access. Rotational impoundment management, in which the marsh is minimally flooded during summer but is flap-gated to reintegrate impoundments to the estuary for the rest of the year.
Biological Control Biological control includes use of many predators: - dragonfly nymphs and other indigenous aquatic invertebrate predators such as Toxorhynchites spp. - predacious mosquitoes that eat larvae and pupae; however, - mosquito fish, Gambusia affinis and G. holbrooki. - Naturally occurring Fundulus spp. and possibly Rivulus spp. , killifish Mosquito fish are indiscriminate feeders that may eat tadpoles, zooplankton, aquatic insects, and other fish eggs and fry. - The entomopathogenic fungus, Laginidium giganteum, has been registered for mosquito control by EPA under the trade name Liginex, - The pathogenic protozoon, Nosema algerae, (Not available). - Entomoparasitic nematodes such as Romanomermis culicivorax and R. iyengari are effective; - A predacious copepod, Mesocyclops longisetus, preys on mosquito larvae and is a candidate for local rearing with Paramecium spp. for food.
Genetic control � Genetic control will make use of male insects which will be sterilized and released into the field where they mate with several females but without producing any offspring. This is being tested and with the developments in biotechnology, it may be the technique of the future. � In the insect world, the female once mated will not go for mating with another male.
When did we start using insecticides? At the beginning of World War II (1940), insecticide selection was limited to several arsenicals, petroleum oils, nicotine, pyrethrum, rotenone, sulphur, hydrogen cyanide gas, and cryolite. � At the beginning of World War II (1940), our insecticide selection was limited to several arsenicals, petroleum oils, nicotine, pyrethrum, rotenone, sulfur, hydrogen cyanide gas, and cryolite. It was World War II that opened the Modern Era of Chemical control with the introduction of a new concept of insect control --synthetic organic insecticides, the first of which was DDT. � � It was World War II that opened the Modern Era of Chemical control with the introduction of a new concept of insect control --synthetic organic insecticides, the first of which was DDT.
Insecticides � Insecticides are agents of chemical or biological origin that control insects. � Control may result from killing the insect or otherwise preventing it from engaging in behaviors deemed destructive. � Insecticides may be natural or manmade and are applied to target pests in a myriad of formulations and delivery systems (sprays, baits, slow-release diffusion, etc. ).
Insecticides Natural Pyrethrum Rotenone Derris Nicotine Mineral oils Organochlorine compounds DDT, Methoxychlor, BHC, Lindane, Heptachlor, Dieldrin, Aldrin, Toxaphene, Kepone, Mirex Repellents Metadiethyltoluamide Benzyl benzoate Indalone Dimethyl phthalate Ethyl hexanediol Stomach poisons Paris Green Sodium fluoride Organophosphates Chlorthion, Diazinon, Dioxothion, Demethoate, EPN, Malathion (OMS 1), Fenthion (OMS 2), Methyl parathion, Parathion, Ronnel, Trichlorfon, Dichlorvos, Abate (OMS 786), Naled, Gardona, Chlorpyrifos, Fenitothion (OMS 43), Dicaphthon (OMS 214) Fumigants Hydrogen cyanide Methyl bromide Sulfur dioxide Carbon disulphide Carbamates Carbaryl Dimetilan Pyrolan Propoxur (OMS 33) Synthetic pyrethroids Resmethrin Bioresmethrin Pothrin
Inorganic Insecticides They are compounds of arsenic and fluorine but may also include compounds of sulphur and salts of zinc, copper, lead, mercury, chromium and selenium. � Mostly not very selective and not very toxic to insects; large quantities are required for effective control. � Most commonly used inorganic insecticides: copper arsenate, lead arsenate and cryolite; Paris Green, or copper acetoarsenite is a stomach poison; used as larvicides; is applied as 2% dust by mixing with soapstone powder or slaked lime; 1 Kg/ha is recommended. � Arsenials are also important in the control of cattle ticks; �
Organochlorines The organochlorines are insecticides that contain carbon (thus organo-), hydrogen, and chlorine. � They are also known by other names: chlorinated hydrocarbons, chlorinated organics, chlorinated insecticides, and chlorinated synthetics. � The organochlorines are now primarily of historic interest as more are banned. See DDT �
The Callous Spray of DDT • The United States used a lot of DDT during the mid-1900 s • At one point, the US was producing 220 million pounds of DDT a year! In 1958, nearly 80 million pounds of DDT was sprayed onto American farmlands.
Organophosphates OPs is the term that includes all insecticides containing phosphorus. � Other names used, organic phosphates, phosphorus insecticides, nerve gas relatives, and phosphoric acid esters. � All organophosphates are derived from one of the phosphorus acids, and as a class are generally the most toxic of all pesticides to vertebrates. � The OPs are generally divided into three groups--aliphatic, phenyl, and heterocyclic derivatives. �
Fumigants The fumigants are small, volatile, organic molecules that become gases at temperatures above 40 o. F. They are usually heavier than air and commonly contain one or more of the halogens (Cl, Br, or F). Most are highly penetrating, reaching through large masses of material. They are used to kill insects, insect eggs, nematodes, and certain microorganisms in buildings, warehouses, grain elevators, soils, and greenhouses and in packaged products such as dried fruits, beans, grain, and breakfast cereals. � Methyl bromide and others - ethylene dichloride, hydrogen cyanide, sulfuryl fluoride (Vikane®), Vapam®, Telone®II, DD®, chlorothene, ethylene oxide, and the familiar home-use moth repellents napthalene crystals and paradichlorobenzene crystals. Developing countries have to stop MB by 2045 as per Montreal Protocol. � Phosphine gas (PH 3) has also replaced methyl bromide in a few applications. �
Malaria- Interventions If we can control malaria, we will see an acceleration of Africa's development � If malarious areas are free of the disease, family incomes will rise � If there is less malaria in homes, school attendance will increase sometimes dramatically. Tools needed to roll back this cause of suffering and poverty, to banish this obstacle to economic growth. � Insecticide treated nets in the home reduce transmission and prevent infection. � Indoor spraying with safe insecticides prevents infection. � Treatment during pregnancy protects the mother's health and improves birth weight. � Rapid diagnosis and early treatment of someone with malaria shorten the illness and reduce death rates. � These interventions appear simple. Ensuring their success is not. To be effective they must reach all at risk.
Lymphatic Filariasis Debilitating parasitic disease � Caused by nematode worm Wuchereria bancrofti � Transmitted by mosquitoes- Culex and Anopheles spp. � Consequences: - disability(elephantiasis) - Social and cultural stigma - Discomfort due to acute bacterial adenolymphangitis �
Lymphatic Filariasis
Yellow Fever � Acute communicable disease caused by arthropod – borne flavirus (B arbovirus) � Jaundice is prominent sign � Disease is distributed in two epidemiological patterns Ø Urban – man to man transmission by Aedes aegypti Ø Sylvatic – transmission b/w monkeys anf from monkeys to man via Ae. africanus and Ae. lutheocephalus
Dengue Fever � Dengue fever is acute infection caused by Arboviruses transmitted by Aedes mosquitoes � May have similar epidemiological pattern with YF. � However, discovery of Ae. albopictus in 1991 in Nigeria resulted in replacement of Ae. aegypti may have changed the epidemiological pattern
Integrated Vector Management IVM is a process of evidence-based decision making procedures aimed to plan, implement, monitor and evaluate targeted, cost-effective and sustainable combinations of regulatory and operational vector control measures. � IVM has a measurable impact on vector borne disease transmission risks. It adheres to the principle of subsidiary, inter-sectoral partnerships and adds on selective vector control, the attributes of environment friendly interventions, and sustainability. �
The concept of Integrated Vector Management � builds on selected vector control which was defined by WHO Expert Committee on Malaria as following: the targeted use of different vector control methods alone or in combination to prevent or reduce human vector contact cost-effectively, while addressing sustainability issues (WHO, 1997).
IVM Attributes IVM has the following attributes: - environmentally sound, - inter-sectoral, - selective, - targeted, - cost-effective and - sustainable. IVM involves the utilization of a range of interventions including environmental management and the safe and judicious use of insecticides and biological control agents. �
IVM Components INTERVENTION TARGETS TYPE a) Environmental Appropriate Mosquitoes, black flies, snails, Management environmental changes etc. and communal hygiene and sanitation * b) Biological Control c) Chemical Control d) Genetic Control REQUIREMENTS Appropriate tools and habitat management. Larvivorous fishes, fungus & other microbes, nematodes etc Predators parasites Competitors Larviciding Mosquitoes Black flies Microbial larvicides, Local Fishes e. g. Tilapia, guppies etc Snails Efficient predators and competitors Mosquitoes, Black flies, snail vector etc Space/Outdoor spraying Mosquitoes Recommended and approved insecticides, Neem & other herbal insecticides, Insect Growth Regulators (IGR) and approved application equipments Pyrethroids, other recommended and approved insecticides, Personal Protective & approved and appropriate equipments Indoor Residual Spraying Vectors of malaria, lymphatic Filariasis, Leishmaniasis Pyrethroids, other approved insecticides Insecticide-treated nets Vectors of malaria, Leishmaniasis, lymphatic Filariasis, trypanosomiasis Personal Protection Mosquitoes, flies, fleas Pyrethroids & appropriate materials Sterile Insect Technology Well-equipped laboratory (long term) Mosquitoes, Tsetse flies, black flies Insecticide coils, mats, repellents, natural products etc
Vector Control Services This vector control unit will consist of a core group with entomological, epidemiological and environmental skills. � The role of the Vector Control Unit will be to provide the overall strategic and technical guidance to LGAs, for planning, implementation, monitoring and evaluation of vector control activities on the basis of information from epidemiological and environmental health services. � The State Ministries of Health will have to include vector control and environmental health skills. � On the basis of the orientation received from the vector control services, the State Team will prepare and implement integrated vector management plans with technical support and advice from the national level. �
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