INTRODUCTION

Arthropods are the most successful and the largest animal invertebrate group of metazoan creatures on earth with segmented bodies having six or more jointed legs^1,2. Among all known living animals on the earth, almost 75% belong to arthropods³, moreover, they are found ubiquitously. Arthropods range from less than 1 cm to 3.2 m like giant king crab⁴. Most familiar arthropods include butterflies, beetles, flies, fleas, ticks, mites, ants, bees, spiders, scorpions, shrimps and crabs. Regarding their importance it is stated that life on earth would end very quickly without arthropods. These invertebrates play a great role in pollination of the flora, which in turn supply food and also maintain the clearance level of air and water, furthermore, they also act as majestic recycler and decomposers, along with marvelous food source⁴.

In relation to their life style small numbers of arthropods have developed the ability to parasitize a wide range of hosts including other arthropods too¹. Some arthropods have biting habit, which can make the living awkward both for humans and animals. Arthropods are also indirectly responsible for death of many people and animals⁵. Stored food products may be damaged or contaminated by live or dead insects or their faeces, odours, webbing or cast skins⁶. Most of insects act as vectors of different pathogens. There are also a number of arthropods that cause harm through their venom⁷. Hematophagous arthropod vectors, such as mosquitoes, ticks and flies are responsible for transmitting bacteria, viruses and protozoa between vertebrate hosts, causing deadly diseases such as malaria, dengue fever and trypanosomosis^5,8. Mortality caused by arthropods-borne diseases in human being was more than all other factor if combined combined at the beginning of 20th century. Globally, some of the important emerging vector-borne-zoonoses are simian malaria, Chagas disease and leishmanosis. Out of 1,415 human pathogen species, 868 (61%) are known to be zoonotic. Likewise of this total, 177 (13%) pathogen species are considered emerging and re-emerging. The species which are regarded as emerging or re-emerging for protozoa, the counts were 58 and 14 (25%) and for helminths, 289 and 10 (3%), respectively⁹.

In the past 15 years more than 20% of gross national products in African continent was abridged by malaria alone¹⁰. It has been observed that malaria caused more than one million deaths, mostly children, moreover 300-500 million clinical cases of malaria are reported annually. Arthropods have played a very important role in their relationship with man and animals. Historical records from pre biblical times revealed that these creatures played havoc with living beings by causing annoyance, worries and acting as vectors of various diseases¹¹. As a result of their activity, arthropods may have a variety of direct effects on their hosts¹², which include: Blood loss, myiasis, entomophobia, annoyance, social nuisance, envenomization, dermatitis, pruritus, toxic and allergic responses.

Besides causing various direct effects ecto-parasites play crucial role in scattering of deadly pathogens by acting as vectors of protozoa, bacteria, viruses and helminths. In contrast to mechanical transmission, biological transmission requires a period of time between acquisition of the pathogen and maturation of infection. The vector may then remain infective for the remainder of its life¹. A pathogen may reside and multiply in alternative vertebrate hosts, which are immune or only mildly infected by it e.g., Yersinia pestis, which is responsible for bubonic plague. It is endemic in wild rodents but in domestic rats and humans it is transmitted by fleas (Xenopsylla cheopis). Details of individual arthropods of public health significance are discussed as under.

Mosquitoes: Mosquito-borne diseases are among the world’s leading causes of illness and death, moreover, despite great strides over the last 50 years, the World Health Organization (WHO) recorded more than 300 million clinical cases each year. Both natural as well as artificial circumstances result into stagnant water, which are favorable to mosquito reproduction. They need still or sluggish moving water for the completion of larval and pupal stages^13-15. For example, Aedes aegypti breeds primarily in man-made water containers such as automobile tyres, metal drums, etc. or they breed in tree holes and leaf axils^16,17. For the profusion of mosquitoes and the frequency of mosquito-borne infections three main aspects are needed i.e., warmth, rainfall and relative dampness¹⁸.

For the effective growth of all tropical mosquito species the most favorable temperature ranges between 25-27°C¹⁹. Further within the mosquito vectors there is strong temperature dependence for parasite survival and development. For example, it has been seen by Oaks et al.²⁰ that the time required for the sporozoites of Plasmodium falciparum to get into the salivary glands is inversely proportional to the air temperature with a difference of 14 days between 30 and 10°C. The prevalence of mosquito borne infections correlate with rainfall patterns and season²⁰.

Low level of rainfall tends to generate less reproduction habitats and high rainfall causes washing away of the eggs²¹. Large number of the unfamiliar species having human health impacts are either relatively recently appeared (e.g., Aedes albopictus, A. japonicus, A. koreicus and Ochlerotatus atropalpus)²² or in the last 10 years they have strongly spread (e.g., Ambrosia artemisiifolia)^23,24.

Simian malaria, which is caused by Plasmodium knowlesi is transmitted by Anopheles laten that feeds on monkeys. This malaria was first noticed among humans in 2004, which now poses a major threat in South East Asia region. It is usually misdiagnosed with P. malariae, which is a benign condition²⁵. In India, simian malaria was first reported in 2013 in Andaman and Nicobar islands. It has been reported that mono infection with P. knowlesi contributes to 5% and co-infection with P. falciparum occurs in 12% drug resistant associated with P. falciparum infection in Andaman and Nicobar islands. Presently, one of the most important Aedes aegypti borne viral diseases affecting people in terms of both infection rate and death is the dengue fever. This virus belongs to the genus Flavivirus within the Flaviviridae family²¹. Across the globe it has been seen that about 2.5 billion people are at risk of this vector borne infection. Out of these more than 975 million live in urban areas in tropical and sub-tropical countries such as in Southeast Asia, the Pacific and the Americas alone²⁶. Due to high infection rate this disease, it has been seen that more than 50 million new cases occur each year, resulting into hampering of the health status of children. The mortality rate is still exceeding 5% and about 500,000 hospitalizations occur for dengue haemorrhagic fever^27,28. The annual average of dengue cases had double between 1990-1999 and 2000-2004²⁶. Appearance of dengue hemorrhagic fever/dengue shock syndrome had occur due to the bite of infected Aedes aegypti, after hurricane due to unnecessary water lodging has also led to hyperendemicity²⁹. Moreover, diptera of the genus Aedes spp. also have drought-resistant eggs, which are able to withstand long journeys and enter Europe associated with used tires or lucky bamboos, which are imported from Asia^22,24.

Repellents for mosquito control: Based on the different types, quantity of perspiration and rubbing of the skin and the level occurrence of mosquitoes, repellents can prove protective for one to 5 h for humans body³⁰. Delicate body parts such as eyes, nostrils and lips should always be kept away from repellents, moreover, they can also damage plastics, synthetic fabrics and certain painted or varnished surfaces. Repellents used in commercial products include diethyltoluamide-containing active ingredient as N, N-diethyl-3-methylbenzamide (DEET), permethrin, citronella, Eucalyptus and other natural ingredients. The DEET is the most common and effective repellent³¹. For children’s the concentration of less 15% and in adult’s product a concentration of 10-35% of DEET is recommended³². Application of permethrin should always be done to outer parts and should not be applied to skin-clothings. Moderate protection with benefits against mosquito bites also obtained with oil of citronella, Eucalyptus and other natural ingredients³³. All of these products are less effective than DEET. According to the United State Environmental Protection Agency (EPA), DEET is used annually by almost 40% of Americans and by about 200 million persons worldwide (www.muskol.ca/about_deet.htm).

Other methods for repelling or trapping mosquitoes: Studies have shown that reduction or elimination of biting activity and other behavior of mosquitoes are not significantly affected by any electronic or ultrasonic repeller devices³⁴. Traps which use ultraviolet light as an attractant (black light bug zappers) are also not effective in reducing the biting mosquito population. However, there are modifications of this trapping concept presently being marketed that use CO₂ octenol and other chemicals to attract mosquitoes more effectively. The scented geranium plant, Pellargonium spp., more commonly known as the Citrosa ‘Mosquito fighter’ plant has not proven to be effective in repelling mosquitoes from an area. Moreover mosquito management at home level should be adopted: Water should not be allowed to stand in tin cans, plastic containers etc., clean roof gutters annually, use landscaping to eliminate standing water, use netting avoid unnecessary lighting^30,33.

Biological control: As biological control does not cause chemical pollution, it is considered as a better method for mosquito control by many people. The most commonly used predators of mosquitoes include:

Ticks: Ticks transmit a variety of pathogens including protozoa, rickettsia, bacteria and viruses to both humans and livestock⁴³ and cause substantial economic damage worldwide^44-46. Macroclimatic factors play a major role on the seasonal population dynamics of ticks and thus on tick borne diseases⁴⁷. Lyme disease, rocky mountain spotted fever, ehrlichiosis, babesiosis, tularemia, tick paralysis, tick-borne encephalitis and mountain tick fever are some of the common diseases of humans transmitted by ticks. Lyme disease is the most common vector-borne disease of humans in the United States and Europe^48,49. Annually 20,000-27,203 cases are reported to CDC (http://www.cdc.gov/lyme/stats/maps/interactiveMaps.html).

Mosquitoes suck blood several times but on the other hand, ticks act as blood feeders only once per stage of their life cycle. However, they can take large amount of blood meals equivalent to 10-100 times more to their own body weight¹⁰. The primary hosts of Ixodes scapularis that carries Borrelia burgdorferi, which causes lyme disease in humans are the white-footed mice (Peromyscus leucopus) and white-tailed deer (Odocoileus virginianus)⁴⁸. During their life cycle, different ixodid species may use one, two or three different hosts^50-53 Rocky mountain spotted fever is most important rickettsial disease affecting about 1,000-2,000 cases per year and is characterized by headache, fever, chills, malaise, gastrointestinal symptoms, which sometimes lead to coma and at last death⁴². Regarding human monocytic ehrlichiosis case reported in 2012 were 1,128 with 1.1% fatality, primarily affecting the hosts leukocytes. Cases recorded in human granulocytic anaplasmosis were 2,389 in 2012 affecting RCBs of host⁴². Up till 1969 in USA alone more than 300 cases of babesiosis were recorded in humans. A total of 716 confirmed cases were recorded in 2012 depicting malaria like symptoms. Humans affected by tularemia (rabbit fever) in 2012 were 149 (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6153a1.htm). Tick-borne encephalitis is a complex disease of closely related virus; it may lead to severe motor dysfunction. Tick paralysis is caused by salivary toxin of tick and it leads to acute, ascending, flaccid motor paralysis¹.

Tick and ticks borne diseases control measures include managerial control, chemical control, biological control and immunological control. Due to confrontation against chemical agents, biological and immunological controls are gaining significance now-a-days. In biological control many agents have been tested and provided excellent results such as bacteria: Bacillus thuringiensis, B. cereus (both target Argas persicus, Hyalomma dromedarii and Ornithodoros erraticus), Proteus mirabilis (targets Dermacentor andersoni), Cedecea lapagei (targets Boophilus microplus). Fungi: Beauveria bassiana (targets B. microplus), Metarhizium anisopliae (targets Rhipicephalus sanguineus)⁵⁴. Entomopathogenic nematodes: Hetererhabditis indicus (targets Boophilus annulatus, Hyalomma dromedarii and Hyalomma excavatum) and Steinernema riobrave (targets Amblyomma americanum and Amblyomma cajennense, Rhipicephalus appendiculatus, R. sanguineus)⁵⁴. In immunological control, many vaccines have been tried to elicit an immune response against ticks such as TickGUARD (B. microplus), TickGARD plus (E. coli expressed BM86+BM91), Gavac^TM (B. microplus)⁵⁵.

Mites: Scabies mite (Sarcoptes scabiei) is distributed worldwide¹. The mite gets transmitted by contact, burrows into the skin on the webbing side of fingers, later spreading to the wrists, elbows and the rest of the body⁵⁶. The buttocks, women’s breasts and external genitalia may be involved. Effective diagnosis of mites can be made by their characteristic typical rash and the burrowing tunnel, in which mite reside can be made easily visible by first coating black ink on the skin of animal followed by its wiping⁵⁷. The mite may spread from humans to animals and vice versa. Treatment involves swabbing of the whole body from the neck down with 1% malathion or benzene hexachloride (crotamiton for infants)¹. Moreover, it can be systemic (e.g., oral selamectin for S. scabiei) or topical (e.g., amitraz dip for D. canis). Treatment of infestations of rabbits by Notoedres cati var. cuniculi has been successfully carried out by systemic application ivermectin⁵⁸ as well as topical application of deltamethrin⁵⁹ in India. In Brazil soap containing tetramethylthiuram monosulfide was effectively used in the treatment of cat fur mite (Lutzomyia radovskyi)⁶⁰. Parasitic dermatitis results from canine demodicosis and sarcoptic mange dogs^61-63. In the same manner, canines infected with sarcoptic mange in and endoparasites were treated with a single subcutaneous injection of doramectin 1% (0.3 mg kg‾¹)⁶⁴. However, the resistance has been reported for allopathic drugs for demodicosis. Homeopathic medicines have been used successfully in such cases which are refractory to allopathic drugs⁶⁵. The use of insecticide-treated bed nets has also been proven to be effective in protecting humans against L. longipalpis bites⁶⁶, but this strategy is not currently used in Brazil as part of the national programme against zoonotic visceral leishmaniosis. Chiggers (larvae of red mites or harvest mites) (Trombiculidae) are an important group of ectoparasites affecting humans. Before dropping off chiggers use enzymes present in their saliva and feed on partially digested skin cells after piercing the skin near a hair follicle. They neither feed on blood nor burrow into the skin of the animal⁶⁷. Piercing activity along with presence of enzymes cause pruritic eruption and its strength depends on the sensitivity of the host mammal and may lead to fever. Chigger bites can be controlled by using insect repellents DEET. In South Asia, India, Pakistan, Sri Lanka chiggers are the vectors for scrub typhus (Orientia tsutsugamushi), a rickettsial disease that can (rarely) be life-threatening. Scrub typhus is prevalent all over India, but since 2004 it has shown re-emergence in places like Himachal Pradesh, Jammu and Kashmir, Rajasthan, Andhra Pradesh, Uttarakhand, Pondicherry, Kerala, Goa, Delhi and West Bengal⁴². This disease is often missed out due to non-specific symptoms, lack of awareness and non-availability of diagnostic tools. Most of diagnoses are based on high suspicion. The chance for mortality may rise to 30% if not treated⁴². Another peculiar feature is that it is not transmitted by bite but when the larva gets accidentally landed on human skin and gets crushed.

Lice: The relation of lice and human beings is very old as some of the Egyptian mummies were seen to be effected with lice. Moreover, phylogenetic evidence also put forward that lice-humans adaptation was about 5.6 million years ago when the ancestors of chimpanzees and humans depart from each other⁶⁸. Three types of sucking lice are important for human health: Pediculus humanus var. capitis (head louse), P. humanus var. corporis (body louse) and Pthirus pubis (crab/pubic louse). Lice are very host specific, both sex are blood feeders and depart one host only to infect another host⁶⁹. Louse typically feeds 4 times a day (die if away for more than 2 days) and molts 3 times in 10 days after hatching. In the developed world, 2-10% of children are infested with head lice^70,71. Disease such as epidemic typhus (by body lice) is caused by Rickettsia prowazekii, which is a category B bioterrorism agent and an obligatory intracellular alphaproteobacteria⁷¹. Other disease transmitted by lice include Borrelia recurrentis, which causes fever with long bone shooting pains and in world war I, it affected 1,000,000 individuals. Trench fever (Borrelia quintanas) was also dominant in world war I.

Louse-borne relapsing fever affected 4,972 cases with 29 deaths in 1971⁴. Head lice are known to mechanically transmit Staphylococcus auereus and Streptococcus pyogenes⁷². Diagnosis is based on finding eggs or nits (eggs) in seams of clothing⁷³. Coarse hairs of pubic area in adults or eye lashes in children are sometime get infested with pubic lice (crab lice)¹. Transmission in adults is usually by sexual contact. Confirmatory diagnosis can be done by finding lice or nits in the infected area of mammal.

To decrease the chance of being infected with head lice hair should be regularly cleaned with shampoo having 1% benzene hexachloride. It should be always kept in mind that some time benzene hexachloride can be toxic, so other product such as mixture of pyrentins (0.2%) and pipronyl butoxide (2%) or copper oleate are also effective and they are less toxic too^70,73. The permethrins are incredibly safe with only rare cases of asthma exacerbations noted in individuals with severe ragweed allergy⁷¹. It is effective against head louse, but in recent years the human louse has become increasingly resistant to them. Therefore, many doctors are using malathion, a common pesticide that in diluted concentration is very effective against the louse and is available over-the-counter in many countries with wider safety margin mainly in children⁴.

Temperatures above 100°F or below 75°F reduced the fecundity of body lice targeting mainly its hatchability potential. Long term storage of outfits, without treatment, will help in killing all eggs, any if any young emerges it will die soon⁶⁹. Washing clothes in hot water (60°C) also helps in killing the lice. For the effective treatment of crab louse many commercial preparations are available, which can also be used for head or body lice. Plucking with forceps is useful for nits and lice removal from eye lashes. Some ointments having physostigmine (0.25%) or yellow mercury oxide are effective¹. Biological control can be used and an alternate to the chemical method. Chlamydospores of fungus (Metarhizium anisopliae) when applied in the fleece of animals are consumed by the louse, after some time spores sprout and grow into the body of a louse resulting in its instant death. Flower extract from Chrysanthemum cincerariaefolium stimulates the nervous systems of lice and in the end result in its killing.

Fleas: Worldwide, more than 2,574 species of fleas parasitize mammals and birds. They belong to 16 families and 238 genera, but only a minority is synanthropic, that is they live in close association with humans⁷⁴. The most common being the cat flea (Ctenocephalides felis), dog flea (C. canis), human flea (Pulex irritans) and oriental rat flea (Xenopsylla cheopis)¹. Plague, caused by Yersinia pestis is a zoonotic disease primarily affecting rodents, but that can affect human beings. It has been the cause of three recorded pandemics⁷⁴. Moreover, small outbreaks continue to occur throughout the world; around 2000 cases are reported annually⁷⁵. The oriental rat flea is the primary vector of bubonic plague and murine typhus⁷⁶. On the whole 3 forms of plague are recognized: bubonic, septicemic and pneumonic. Septicemic and pneumonic are secondary to bubonic form. Pneumonic is most dangerous form⁷⁷. India witnessed outbreak of plague as early as 1612 in Agra. In 1994 there was an epidemic of plague in beed district of Maharashtra and Surat district of Gujarat. It was bubonic type in beed district and pneumonic type in Surat. Later outbreaks were reported in Shimla district of Himachal in 2002 and in Uttarakhand in 2004.

The three steps to effective flea management are treatment of infested pets, vacuuming and cleaning of infested premises. Since most flea problems originate from an infested cat or dog, elimination of fleas from the pets is the first and most important step. The jigger flea or chigore (Tunga penetrans) is a serious pest in the tropical and subtropical regions of America and Africa. Diagnosis of tungiasis is rare in North America⁷⁸. Moreover various pathogenic bacteria have been isolated from tungiasis lesions: Clostridium tetani⁷⁹, Streptococcus pyogenes, Pathogenic Staphylococcus aureus, Klebsiella aerogenes, Enterobacter agglomerans, Escherichia coli and other Enterobacteriaceae. Both sexes feed on blood. The female flea, after insemination, burrows itself in the skin of the toes and the sole of the foot¹. The female swells to the size of a pea, produces eggs and dies in the tissue. There is local reaction to the bite and the eggs and dead flea produce reaction⁷⁶. The infested tissue can get infected and gangrenous. Treatments are symptomatic.

Flies: The house fly’s (Musca spp.) filthy habits along with its persistence for invading homes and feeding on human food enable the house fly to spread many intestinal diseases such as dysentery and diarrhoea. They are not only the source of annoyance but also mechanical transmitters of various pathogens due to their habit of visiting decaying organic material. The pathogens are carried on the hairs of feet and body or regurgitated as salivary vomit during subsequent feeding¹. A number of Musca species are associated in the spread of diseases including conjunctivitis and anthrax. They also act as intermediate hosts for some of the helminths.

There are four basic principles of pest management important in controlling house flies: sanitation, exclusion, non-chemical measures and chemical methods¹. These are listed in order of lasting effectiveness. Regardless of advancements in chemical control, sanitation is still the best method of controlling filth flies in and around the home. Do not let garbage, manure or other decaying organic matter accumulate in the open and make sure garbage cans have sound bottoms and tight fitting lids⁸⁰. Flies can be kept outside of homes by the use of window and door screens. Make sure screens are tight-fitting without holes. Try to make all screen doors open outward. In areas with high humidity, screens last longer when made of copper, aluminum or plastic^80,81. A fly swatter is an economical control method for the occasional fly control⁸⁰. Fly traps may be useful in some fly control programmes if enough traps are used, if they are placed correctly and if they are used both indoors and outdoors⁸². One trap should be placed for every 30 feet of wall inside buildings, but not placed over or within five feet of food preparation areas. Recommended placement areas outdoors include near building entrances, in alley ways, beneath trees and around animal sleeping areas and manure piles⁸¹. Chemical control includes the applications synthetic pyrethroid (i.e., deltamethrin, cyfluthrin, lambda-cyhalothrin, cypermethrin, sumithrin or tralomethrin) and should be applied in the form of a residual or surface spray when flies begin to appear¹. Unfortunately, because insecticides are broken down by sunlight, the residual effect of the material will be greatly decreased and may not kill flies much beyond several days or a week⁸⁰. Release the mist from the aerosol for a few seconds around the room and keep the room closed for 10-15 min⁸². Residual sprays providing 2-4 weeks control with 1 treatment may be applied to fly-resting surfaces. Other measures for control of adult flies include use of insecticide resin strips or various fly baits⁸¹.

Myiasis: Myiasis, a noun derived from Greek (mya or fly) was first proposed by Hope to define diseases of humans caused by dipterous fly larvae, as opposed to those caused by insect larvae in general⁸³. Myiasis is the parasitism of a vertebrate host by the larva of a dipteran fly⁸⁴. Human cases are rare but happen especially in tropical countries⁸⁵. Species that cause myiasis are cochliomyia (Screw worm fly), Calliphora, Oestrus, Sarcophaga and Gastrophilus, etc.⁸⁶. Human myiasis can presented as cutaneous myiasis, anal myiasis, genito-urinary myiasis, nasopharyngeal myiasis, ocular myiasis, body cavity myiasis, wound myiasis, aural myiasis and intestinal myiasis⁸⁷. Depending upon fly larvae myiasis has been classified in to three types including obligatory myiasis (true parasitism), facultative myiasis (oppurtunistic) and accidental myiasis (accidental ingestion of larvae)⁸⁸. Larvae can burrow through necrotic or healthy tissue using their mandibular hooks aided by proteolytic enzymes⁸⁷. Cutaneous myiasis may require surgical confiscation of burrowed larvae⁸⁹. Eggs and maggots may be washed from hair, skin and wounds with soap and water⁹⁰. Urinary myiasis usually clears itself. Purgation with anti-helminths may be necessary for gastrointestinal myiasis.

In human myiasis the flies involved are Psychoda albipennis (urogenital myiasis), Telmatoscopus albipunctatus (intestinal myiasis), Hermetia spp. (furuncular myiasis, intestinal myiasis), Scenopinus spp. (urogenital myiasis), Eristalis tenax (urogenital myiasis, intestinal myiasis), Megaselia scalaris (intestinal myiasis, urogenital myiasis, wound myiasis), Drosophila melanogaster (nasal myiasis, ocular myiasis), Piophila casei (urogenital myiasis), Dermatobia hominis (furuncular myiasis), Alouattamyia baeri (pulmonary myiasis), Hypoderma lineatum (migratory myiasis), Hypoderma tarandi (ocular myiasis), Lucilia sericata (wound myiasis), D. hominis (external ophthalmo-myiasis), C. hominivorax (orbital myiasis)⁹¹.

Black flies: Black flies are amongst the smallest blood-sucking dipterans⁹². There are numerous species of black flies out of which the important ones are Prosimuliim mixtum, Cnephia pecuarum and S. meridionale⁹³. They usually breed in well-aerated water bodies such as swiftly moving shallow mountain torrents⁵³ or sunlit, fast flowing rivers in the tropics⁹⁴. Onchocerciasis or river blindness is caused by the helminth Onchocerca volvulus of the family Filariidae, whose larvae are transmitted between humans by the black flies⁹⁵. Onchocercosis is the second leading cause of blindness in the world with 96% of the affected people living in 30 countries in sub-Saharan Africa (Yemen) with the remainder in six countries in Latin America⁹⁶. This disease has left more than 37 million people infected and millions blind in African countries⁹⁷. Several programmes such as the onchocercosis control programme in West Africa⁹⁸, the onchocercosis elimination programme for the Americas⁹⁹ and the african programme for onchocercosis control¹⁰⁰ targeted this dreadful disease.

Tsetse flies: The tsetse is a prehistoric species that originated about 100 million years ago¹⁰¹. Tsetse is derived from African word meaning ‘the fly destructive of cattle’. Tsetse flies (Glossina spp.), which are found only in Africa transmit various protozoan parasites of the genus Trypanosoma, which cause sleeping sickness in humans and ‘nagana’ in domestic animals¹⁰². These flies appear like honey bees, 7-13 mm long, yellowish brown/black in color. They are found mainly in African countries between 15°N and 20°S latitude¹⁰². There are 30 species or subspecies of tsetse, classified into three groups: The fusca group (13 species), found mostly in forests, the palpalis group (5 species), found in forests and riverine vegetation and the morsitans group (5 species); found in woodland areas of Savannah regions¹⁰³. Only Savanna and forest flies affect humans. Human sleeping sickness is caused by Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, which threaten up to 60 million people in 36 countries of sub-Saharan Africa¹⁰⁴. Uganda is the only country in which both species are present¹⁰⁵. The T. b. gambiense is usually transmitted by tsetse of the palpalis group and occurs mostly in cultivated lands within proximity of pools of water in Western and central Africa, it is a disease adapted to humans, although other animals-especially domestic ones may be important reservoir hosts¹⁰⁶. The T. b. rhodesiense, which is the more virulent of the two, is usually transmitted by tsetse of the morsitans group and occurs primarily in the Savannah woodlands of Eastern and central/Southern Africa^107,108, it is a disease that occurs naturally in a large number of domestic and wildlife hosts¹⁰⁹.

In humans, as the disease progresses, the parasite crosses the blood-brain barrier and invades the central nervous system, causing neurological problems¹¹⁰. Compared to other arthropod vectors such as mosquitoes, tsetse flies have a very low reproductive rate and a longer life expectancy¹⁰⁶. The mortality and reproductive rates of tsetse flies are highly dependent upon microclimatic conditions with high survival rates in cool, moist areas¹¹¹. Animal trypanosomosis occurs more or less throughout the area of Africa inhabited by one or more species of tsetse (an area of approximately 10 million km²), while human sleeping sickness, which has a much higher threshold for transmission¹¹², occurs only in a relatively few, but very persistent, disease foci.

Sand flies: Among the most important emerging and resurging vector borne protozoan diseases, leishmanoses stand second only to malaria in terms of numbers of people affected¹¹³. Among >800 species of sandflies recorded, 98 are proven or suspected vectors of human leishmanoses; these include 42 Phlebotomus species in the old world and 56 Lutzomyia species in the new world¹¹⁴. Visceral leishmanosis (kala-azar), mucocutaneous leishmanosis and cutaneous leishmanosis are three diseases caused by Leishmania that spread through the bite of about 30 different species of sandflies¹⁰⁸.

The flight speed of phlebotomines is considerably slower than that of mosquitoes and is <1 m sce‾^{1 115}. They are unable to fly at wind speeds higher than this rate, which is the main factor limiting the range of their dispersal¹¹⁴. Studying their life cycle is complicated because the larvae, which are tiny, are very hard to find, even in areas of high disease prevalence¹¹⁶. About 88 countries are affected with leishmanosis¹¹⁷. Leishmanosis is primarily a zoonotic disease affecting mostly rodents and dogs and humans are incidental hosts. Factors such as deforestation, population migration from endemic rural areas and increased population density in areas with low sanitation have caused a resurgence of leishmanosis by increasing the contact between the vectors and the hosts¹¹⁷.

Visceral leishmaniosis (VL): In the new world visceral leishmanosis is recorded as endemic in 12 countries¹¹⁸. In the past, VL has been considered a rural disease caused by L. chagasi in semi-arid tropical areas in which L. longipalpis was recognized as the sole vector¹¹⁹. The majority of the VL cases in the new world occured in Brazil. An early proposition that the cause of VL in the new world is certainly L. infantum was confirmed by a present continent-wide DNA microsatellite investigation of parasite populace¹²⁰.

Cutaneous leishmaniosis (CL): Prior to the 1960s, CL was primarily restricted to forested areas¹²¹. In Mexico the condition of CL is widely recognized as ‘ulcera de los chicleros’ and is also nominated as ‘guerrilla’s sore’¹²¹. For the establishment of Lutzomyia vectors in Venezuela and Columbia deforestation and the replacement of primary forest by monocultures, such as coffee farming had played a crucial role^122,123. Urbanization has greatly contributed to the emergence and increase of CL in the new world¹²⁴. The disease has been spreading in urban cities in Brazil¹²⁴.

Phlebotomus papatasi is also known to be a vector of other human pathogens, such as Bartonella bacillisformis (Carrion’s disease), which has two clinically distinct phases: An acute or haematic phase, known as ‘Oroya fever’ and an eruptive or tissue phase, known as ‘Peruvian wart’ or ‘Verruga peruana’¹²⁵. Any infected person can experience either one or both phases, which can occured once or more than once during a lifetime. As a consequence death of up to 40% untreated patients occur, on the same time mortality reached approximately 90% when opportunistic illness with Salmonella spp. had take place¹²⁶.

Throughout various armed forces operations such as the Napoleonic wars febrile disease conditions caused by sand flies occurred namely sand fly fever, which is also recognized as Phlebotomus fever, papatasi fever or three-day fever¹²⁷. During World War II (WWII), German troops based in the Mediterranean area suffered from sandfly fever. Naples virus which was first isolated from a febrile patient in Italy in 1944¹²⁸. Additional recoveries have been made in Egypt, India, Iran, Pakistan, Serbia and the former Soviet Union¹²⁹. The prototype strain of Sicilian virus was isolated from humans in 1943. Other isolates were subsequently obtained in Egypt, India, Iran, Pakistan and Afghanistan. No mortality has been recorded in thousands of clinically observed cases¹²⁷. Summer meningitis caused by Toscana virus. Toscana virus was first isolated from P. perniciosus and P. perfiliewi collected in Italy in 1971. The first evidence for the human pathogenicity and neurotropism of Toscana virus was reported more than 10 years after the discovery of the virus¹²⁷. Three vesiculoviruses, Vesicular Stomatitis Virus (VSV)-Alagoas, VSV-Indiana and VSV-New Jersey, cause vesicular stomatitis disease in humans and domestic livestock. Incapability of naturally infected mammal to turn out a constant high-titer viraemia and the ability for transovarial spreading in arthropod hosts are the common features to these three VSVs¹³⁰.

In India Chandipura virus encephalitis was recorded from Chandipura village in Maharashtra in 1965¹³¹. In the Eastern part of state of Gujarat 2nd epidemic with a fatality rate of >75% was reported in 2004^131,132. In Eastern and Northern India i.e., Bihar, Jharkhand, Uttar Pradesh and West Bengal kala-azar is endemic¹³³. Among all these states, 90% of all cases occur in Bihar alone¹³⁴. In these states from time to time epidemics have been reported¹³⁵. Moreover, sporadic cases were recorded from non-endemic areas such as Delhi, Maharashtra, Meghalaya and Karnataka¹³⁶ and also from sub-Himalayan (Kumaon) region of Northern India¹³⁷. In many parts of the world like in Asia, Africa and Mediterranean old world cutaneous leishmaniasis is endemic. Pathak et al.¹³⁸ described a case in an 18 months old male child, who had lesions on lips, nose and chin from India. Impression smears of the lesions revealed L. tropica amastigotes. Interestingly, on the same time a dog in close proximity had similar lesions on its legs and nostrils.