Table of Contents
insect bites and stings
- biting and stinging insects of medical concern include:
- Diptera - mosquitoes, flies and gnats
- Hymenoptera - ants, bees and wasps
- Phthiraptera - lice
- Siphonaptera - fleas
- Hemiptera - bugs including bed bugs
insects in Australia
- mosquitoes are a common problem in Australia with over 300 species, but fortunately Australia is not a malarial country (it was endemic in the tropics but was eradicated in 1981) and only a few species are a concern for disease transmission
- populations of Aedes sagax, Aedes vittiger, and Aedes aculeatus generally boom after floods and rapidly disappear
- life cycle: eggs laid in water or around water; lavae hatch in water live as wrigglers (some eat other species of wrigglers) for a week or so then emerge as adult mosquitoes with a life span of about 3 weeks; as with most flying insects only the females bite and they generally bite a wide range of animals even earthworms;
- Despite there being over 300 species in Australia, only a few pose a serious public health threat.
- in coastal regions of Australia, Aedes vigilax (commonly known as the saltmarsh mosquito) and Aedes camptorhynchus (commonly known as the southern saltmarsh mosquito) are found in estuarine wetlands. These mosquitoes can emerge in huge numbers in summer, are aggressive biters, and can fly many kilometres from wetlands and in coastal regions are the main cause of spread of Ross River virus
- the biggest pest in freshwater areas is Culex annulirostris (commonly known as the banded freshwater mosquito) and is probably the most important species when it comes to spreading pathogens such as Ross River virus, Murray Valley encephalitis virus, and Japanese encephalitis virus.
- the main diseases carried by mosquitoes in Australia are:
- Murray Valley encephalitis virus - north-western Victoria and other states, particularly after floods (eg. La Nina years such as 1951, 1974, 2011) as host is water birds. High subclinical rate with only 1 in 500 becoming ill.
- Kunjin encephalitis virus - rare infections - perhaps 1 a year.
- Ross River virus (RRV) - epidemic polyarthritis, occurs in all states of Australia and is the most common mosquito transmitted disease with over 6,500 cases per year with occasional local epidemics with much higher numbers.
- Barmah Forest virus (BFV) - epidemic polyarthritis; found near Echuca on the Murray River as well as other States, but prevalence is 1/10th that of Ross River infections.
- Japanese encephalitis virus (JEV) was detected for the 1st time in Australia in Feb 2022 in Echuca, southern and western NSW and in Qld
- Buruli ulcer / Bairnsdale ulcer is thought to be spread by mosquitoes in endemic regions - usually areas that are or were swamps
- the most common problem is hypersensitivity reactions (often delayed onset) to the bites although fortunately, anaphylaxis is rare.
the common house fly
- is a household nuisance introduced by the British on the early convict ships
- it prefers to live inside houses and breeds in, and frequents nearby locations (usually within 50m of the house) which tend to be well populated with potentially pathogenic bacteria which the fly can vomit up (this helps dissolve dried substances) or leave excrement on human skin or on objects we touch or, on our food.
- they breed in rotten vegetation or carcasses, including lawn clipping mulch > 2cm deep, compost, rubbish bins, or in sewage.
- each fly carries several million bacteria!
- they have the potential to spread amoebic dysentery, anthrax, cholera, gastroenteritis, parasitic worms, paratyphoid, poliomyelitis, salmonella, shigellosis, trachoma, tuberculosis, typhoid fever, typhus, but fortunately these are quite rare in Australia, and food contamination issues are minimal if proper food handling is maintained.
- they taste with their sticky feet and thus tend to spread bacteria by walking over everything.
- they do not bite
the Australian bush fly
- these are the flies that are really annoying at those Summer barbecues or bushwalks.
- they have become out of control following the introduction of cattle to Australia.
- they only breed in animal dung, and cattle dung is much bigger and more moist than native Australian animal dung and makes a perfect breeding ground (as long as they are not swamped with rain or flood water). This is particularly so in Australia as there are no native cattle dung beetles to control them (native dung beetles tend to be most abundant in Winter), and introduced dung beetles tend to be most abundant in Summer - too late to control the Spring burst of bush fly breeding.
- these breed by their millions in Spring (once maximum daily temps exceed 18degC) across the cattle farms in inner Australia where the Winter is warmer, and then strong winds on warm days blow them to urban areas - thus:
- hot westerly winds blow them into Sydney Nov-Jan with peak numbers occurring in January
- hot northerly winds blow them south to Canberra, Melbourne and Perth, usually with numbers increasing significantly after mid-Nov and peaking in December and lasting until end of January, although some will be present until April in eastern states.
- the winds take them over the sea, and occasionally, they can be a problem in Tasmania.
- Brisbane does not tend to get significant numbers as summer is too wet for them to breed locally and only a few blow in with the westerly winds.
- they are common most of the year in the northern subtropics but numbers fall during Spring, and start to build up with Summer rains to peak in Autumn.
- in drier north-west tropics, the build up is in late Autumn, with a rapid decline in Spring and almost none in the summer 'wet'.
- although numbers are low in desert areas, they are poorly nourished and thus small and annoying most of the year, and the presence of a human will be like a light to a moth!
- bush flies only fly at temperatures above 12degC and fly the most at 27degC. They prefer the sun and avoid indoors or shady areas such as forests unless temperatures exceed 35degC.
- the females are the main ones attracted to humans as they need protein for ovarian function, and thus they like to get to tears, saliva and blood (from open wounds). The smaller ones need the most protein and tend to be the most annoying. Males may annoy humans when they are thirsty.
- they seem to prefer light colours, particularly yellow (whereas house flies prefer red, black, and March flies prefer dark blue)
- they do not bite, do not lay maggots in tissue (only in dung) and rarely transmit disease, although there is a risk of trachoma transmission.
- hopefully the bush fly issue will come under control with the introduction of new dung beetle species.
the blow fly
- these appear to have come to Australia from Africa in the 1880's and had become a serious pest in eastern Australia by 1915, and Western Australia by 1930's, and became a problem in Tasmania by 1957.
- these flies are larger and lay maggots in carcasses, and even on live animals - particularly sheep which is a major problem for farmers, particularly now that these flies have become resistant to chemical sprays.
- they are generally not an issue with humans, but have been known to cause maggot infestations in neglected wounds such as decubitus ulcers in the frail elderly.
- these maggots are the ones preferred by fishermen for bait.
the March fly (Tabanidae)
- these are larger, stout bodied flies which have a painful bite and their saliva which prevents blood from clotting, may cause an allergic reaction.
- they prefer moist ground, and thus tend to be found along streams in late Summer in particular.
- they tend to be very persistent as they suck blood from the human skin and are attracted to dark colours, particularly blue in open sunlit fields
- prevention may require wearing loose, light coloured clothing and use of a DEET-type lotion repellant.
the Stable fly
- these are another biting fly which breeds in hay contaminated with urine and dung, hence their predilection for being around horse stables abd dairies.
- they are a major problem in Perth
- their preference is to bite and feed on the lower legs of cattle.
- they look like house flies but have a needle like proboscis at their mouth.
biting midges ("sand flies")
- NB. these are different insects to the true sand fly such as in north-western NSW and western Queensland and many other countries
- biting midges are small 1-3mm robust jet black insects with piercing and sucking mouthparts that belong to the family of flies Ceratopogonidae.
- they are so small they can get through standard insect screen meshes so use smaller meshes when camping and spray them with insecticides.
- renowned for their nuisance biting associated with tidal sea-water habitats such as coastal lagoons, estuaries, mangrove swamps and tidal flats and prefer calmer waters.
- they breed in wet sand and populations can grow rapidly in warm weather as females produce 30-50 eggs, however, adults only live for a couple of days (whole life cycle takes 3-10 weeks) and can range up to 500m from breeding ground (sometimes up to 5km up valleys if wind carries them)
- tidal waters rising and falling against a vertical surface such as a seawall eliminate the midge problem for the length of foreshore so treated.
- a major problem in northern Australian mangrove areas in particular but also can be problematic on most coastal areas, in Victoria, Gippsland tends to have more of a problem than the western districts
- the biting activity of adult biting midges is mainly limited to the periods of dawn and dusk but may continue overnight and on cloudy days, and seem to be particularly active at low tide on beaches on warm nights with little breeze.
- they will remain inactive through very windy weather, finding shelter amongst vegetation.
- emergence of adults of some species relates to lunar cycles and numbers seem to be higher after spells of hot weather and at neap tides
- Female midges may attack humans in large numbers, biting on any areas of exposed skin, and often on the face, scalp and hands. Some species will blood feed on a wide range of animal hosts.
- bites often cause discomfort, and itching which may be delayed for 12-24 hours
- local residents seem to build up some immunity to the biting.
- in some sensitive people, midges can produce persistent reactions that blister and weep serum from the site of each bite and these reactions may last for several days to weeks.
- lotion formulations of DEET are recommended repellents (but only last 2hrs and need to be re-applied) while fishermen mix zinc cream with various home remedies such as citronella oil, vinegar, etc to help repel them.
- NB. another type of biting midge belonging to the genus Leptoconops appears in the sandstone gulleys of the Berowra-Bobbin l-lead area (just north of Sydney) each year about October and November. This species is typically a daytime head biter, especially inside the ears of animals and around the hairline on humans. lt also bites close to the eye and can cause “bung eye”, a gross but painless swelling of both lids with even complete closure of the eye
bees and wasps
- most of these can sting, and some people may develop potentially fatal anaphylaxis
- 1 in 30 people are allergic, a new vaccine may be available soon to prevent serious reactions
- Australia has over 1,500 species of native bees and of course, the introduced European honey bee to which 1.6% of people are sensitive
- Australian wasps are usually not an issue but the much more aggressive introduced European wasp (Vespula germanica) has become a significant issue as it often stings repeatedly and discharges pheromones to alert other wasps to join in. This wasp reached mainland Australia in Melbourne in 1977 and appears to be restricted to the cool and wet climates of coastal southern Australia.
- there are more than 12,000 species of native wasps in Australia, but the one that is most likely to be encountered around Melbourne suburbs – and most likely to become a pest – is the Common Paper Wasp (Polistes humilis) and of all Australian native insects, native wasps such as the spider wasp and the paper wasp have the most painful stings but thankfully the pain generally resolves within 15 minutes and may be helped by cold water and perhaps acidic fluids such as vinegar 3)
caterpillars and moths
- some moths (eg. Onchogaster lunifer) have barbed, hairy filaments (setae) that are known to cause urticarial rash, corneal inflammation, and facial oedema.
- the moths envenomate humans after people come in contact with the irritant produced by a gland at the base of setae on their feet
- rarely, this may result in osteomyelitis of the phalanges, presumably associated with retention of the setae in the skin of digits
- processionary caterpillars have been associated with outbreaks of paediatric dermatitis, conjunctivitis and respiratory illness.
- Australia is almost the only place on earth that is home to the bull ant family of ants (Myrmecia sp. which evolved some 110 million years ago).
- in the Southern states, bull ants are least active in Winter
- Myrmecia stings are very potent, and the venoms from these ants are among the most toxic in the insect world.
- many of these can deliver painful stings and some people are hypersensitive and are at risk of anaphylaxis, especially to Jack Jumper ants (M. pilosula sp.) to which 2.3% of humans are sensitive
- these ants are capable of stinging through fabric such as cotton gardening gloves
- in Australia, the green-head ant (Rhytidoponera metallica) is the only ant other than Myrmecia species to cause anaphylaxis in people
- the introduced pest, the Argentine ant (Linepithema humile) is much smaller and dominates urban areas but does not inflict a painful bite
- the Iridomyrmex alpinus is a small (~3mm long) aggressive ant found in alpine areas of south-eastern Australia and can be very annoying for bushwalkers camping on mountain peaks as they tend to swarm over bare limbs if they come in proximity to their nests often hidden in ground foliage although they do not sting and their bites are not much more than sharp nips
- other Iridomyrmex sp are mainly found in rural areas (and are almost unique to Australia, having evolved some 12 million years ago) and also tend to swarm and bite, the largest of these are the I. purpureus species group, the “meat ants”
- like ants they are mainly a nuisance as they cause a painful sting which have the risk of anaphylaxis
- large scorpions up to 9cm are increasing in numbers in the dry Mallee region of Victoria due to loss of mammal predators such as bilbies and are mainly nocturnal
- swarming lysianassid amphipods can make a mess of a persons submerged feet if they smell like dead meat, have a bleeding cut or you disturb a swarm feeding on nearby dead fish and you stand still in very cold water which makes your feet numb so you can't feel them biting
Insects of medical concern around the world (not usually in Australia)
other mosquito-borne infections
- dengue fever - although is found in far north Qld but otherwise rare in Australia
- yellow fever
- arbovirus of the flavivirus genus causing acute viral haemorrhagic disease causing jaundice, headache and myalgias and may be fatal
- spread by Aedes and Haemogogus specie
- endemic in tropical areas of Africa and Central and South America but can be spread to other areas
- especially in certain areas at altitudes above 2300m such as in Argentina in the Corrientes and Misiones Provinces ie. Iguazu Falls
- vaccine may not be recommended if you will only be traveling in certain provinces less than 2300m in elevation
- depending on your travel itinerary you may be required to produce proof of yellow fever vaccination when returning to Australia from parts of Argentina
- some airlines require a valid yellow fever vaccination certificate to depart Argentina. Check the yellow fever requirements for Argentina and all countries you'll enter or transit through.
- mainly causes fever and joint pain which may be long lasting and disabling
- outbreaks have occurred in countries in Africa, Asia, Europe (France and Italy), and the Indian and Pacific Oceans including Indonesia 4)
- in late 2013, it was found for the first time in the Americas on islands in the Caribbean.
- it spread to Argentina in 2016 but most cases in Sth America are in Brazil, Bolivia and Colombia
- mainly in the Americas, esp. Puerto Rico and the US Virgin Islands and in Nth Argentina such as Tucuman Province
- Japanese encephalitis virus (JE)
- West Nile virus
- Filariasis is a parasitic disease caused by an infection with roundworms (also spread by black flies)
- lymphatic infection causing elephantiasis, etc - Wuchereria bancrofti, Brugia malayi, and Brugia timori
- subcutaneous filariasis - Loa loa filariasis, Onchocerca volvulus river blindness
- Serous cavity abdominal filariasis - Mansonella perstans and Mansonella ozzardi
- Dirofilariasis - roundworm infection; USA, Europe; causes pulmonary granulomas “coin lesions” 5)
- Saint Louis encephalitis
- Western equine encephalitis
- Eastern equine encephalitis
- Venezuelan equine encephalitis
- La Crosse encephalitis
- Keystone virus
- Rift Valley fever
true sand flies
- in some countries, sand flies can transmit diseases:
- Of the five psychodid subfamilies, only the sand flies (Phlebotominae) have piercing mouthparts capable of taking blood.
- Phlebotomine sand flies (Diptera: Psychodidae) are the natural vectors of Leishmania (Leishmania) spp. (Kinetoplastida: Trypanosomatidae) and phleboviruses (Bunyavirales: Phenuiviridae) in Mediterranean countries.
- Sand flies are tiny insects, 1.5-3.5 mm in length, with a hairy appearance, large black eyes and long, stilt-like legs.
- They can be distinguished from other small flies by their wings, which are hairy and extend at a 40° angle over the body when the fly is at rest or blood-feeding.
- The active season for adult sand flies in Europe spans from April to November depending on the latitude, with warmer regions having longer seasons and up to three generations between May and September
- Feeding activity is influenced by temperature, humidity and air movement (sand flies are weak fliers so even light wind can inhibit flight and reduce biting). Most species feed at dusk and during the night, when temperature falls and humidity rises, although daytime biting can occur indoors in darkened rooms or among shaded vegetation/trees, especially if disturbed by human activity.
- adult sand flies often inhabit rock crevices, caves, and rodent burrows, and in peri-domestic settings rest in cool, dark and humid corners of animal shelters or human dwellings
- Pappataci fever or sand fly fever caused by several strains of a Bunya virus of the Phlebovirus genus
- prevalent in the subtropical zone of the Eastern Hemisphere between 20°N and 45°N, particularly in Southern Europe, North Africa, the Balkans, Eastern Mediterranean, Iraq, Iran, Pakistan, Afghanistan and India.
- Sicilian phlebovirus
- spread by Phlebotomus papatasi mainly in August, although DDT campaigns to Mx malaria have vastly reduced this sandfly in most parts of Europe
- the Toscana virus:
- spread by another sand fly, Phlebotomus perniciosus, and appears to be a common cause of infections in Tuscany and areas of Southern Europe, particularly from Cyprus to Portugal and Spain, and although usually asymptomatic may cause aseptic meningitis in returned travellers.
- Naples phlebovirus:
- is a 3rd strain of Phlebovirus transmitted by flies and the natural reservoir is the Psychodidae sewer fly which transmits the virus to human by bites.
- Leishmania infantum
- is spread in the Mediterranean by the following sand flies: P. alexandri, P. ariasi, P. balkanicus, P. halepensis, P. kandelakii, P. langeroni, P. major, P. mascittii, P. perfiliewi, P. perniciosus and P. tobbi.
- overall, P. perniciosus is the most important L. infantum vector in Europe.
- P. ariasi, P. mascittii, P. neglectus, P. perfiliewi, and P. perniciosus, which are expanding towards more northerly and higher altitude places in Europe associated with climate change 6)
- control in Europe largely relies on preventing vector infestation in dogs using pyrethroid insecticide-impregnated collars and spot-on applications
- 2013-2021 - 467 human cases in Sicily, 71% cutaneous, 29% visceral, while 34% of dogs and 12% of cats were positive! The main region historically with high rates is Catania with highest numbers of sand flies being in Sept 7)
- causes zoonotic visceral and cutaneous leishmaniasis (VL and CL)
- cutaneous leishmaniasis:
- the generally painless skin sores typically develop within a few weeks or months of the sand fly bite, may become a lump which ulcerates and often associated with regional LN enlargement
- visceral leishmaniasis:
- affects several internal organs (usually spleen, liver, and bone marrow) and can be life threatening.
- typically develops within months (sometimes as long as years) of the sand fly bite
- usually have fever, weight loss, splenomegaly, hepatomegaly, anaemia, leukopaenia, and thrombocytopaenia
- Leishmania major and Leishmania tropicum
- restricted to North Africa, the Middle East and Asia Minor
- cause zoonotic and anthroponotic CL
- L. major is absent in Europe despite the vector P. papatasi being widely present, because there are no suitable rodent reservoirs for the parasite
- Borrelia sp
- Rocky Mountain spotted fever - Rickettsia rickettsii spread to humans by Dermacentor ticks. Widespread throughout most of USA and including southern Canada, Central America and parts of South America.
- Colorado Tick Fever - viral infection usually in March-September with peak in June. Mainly found in the high regions of western USA and Canada.
- Babesiosis - Babesia microti is endemic in the Northeast of USA.
- Ehrlichiosis - Ehrlichia chaffeensis is a gram negative coccobacillus causing an illness like Rocky Mounted spotted fever but without the rash. Most commonly foud in the south central states of Missouri, Oklahoma, Tennessee and Arkansas.
- Anaplasmosis - Anaplasma phagocytophilum is a gram negative coccobacillus and the cause of human granulocytotropic anaplasmosis, formerly known as human granulocytic ehrlichiosis. Human infection first described in the late 1990's. Most commonly transmitted in May-June by the deer tick and other ixodes species.
- Crimean-Congo haemorrhagic fever virus (CCHF)
- up to 40% mortality untreated, but rare
- severe fever with thrombocytopenia syndrome virus (SFTS)
- discovered in 2009; mainly in Asia, esp. Japan
- 57 deaths 2013-2017
- Powassan virus
- fever, headache, vomiting, and fatigue, and can cause encephalitis and myelitis
- Tularemia caused by the bacterium Francisella tularensis (also spread by deer flies) - USA
other blood sucking bugs
- kissing bugs
- bite your lips while you sleep and can transmit Trypanosoma cruzi, causing Chagas disease
- may also cause anaphylaxis
- southern USA to northern Argentina
flies of concern
- tsetse fly
- causes African Trypanosomiasis or sleeping sickness
- mainly in sub-Saharan Africa
- deer flies
- Tularemia - USA
- flies causing myiasis
- infestation of human tissue by the larval stage of flies of the order Diptera
- laying maggots under the skin, in wounds including ORIF pin sites, or in mucous regions such as nasopharyngeal, ocular, intra-ocular or genital
- may cause:
- a painful red papule with an opening to allow it to breathe that develops into a furuncle (Dermatobia hominis (human Bot Fly), Cordylobia anthropophaga (Tumbu Fly), Wohlfahrtia vigil, and Cuterebra spp.)
- a migratory dermal swelling +/- regional lymphadenopathy (Gasterophilus spp. and Hypoderma spp)
- wound and body cavity myiasis (Cochliomyia hominivorax, Chrysomya bezziana, and Wohlfahrtia magnifica)
- these may also lead to anaphylaxis especially if the wound is squeezed squashing the maggot or fly
- may result in unusual bacteraemias such as by Wohlfahrtiimonas chitiniclastica
- massive infestations can result in the death usually attributed to “massive toxic shock” or to penetration of viscera or cavities, especially in the head and neck area
- in industrialized countries wound myiasis is a sign of neglected wound care, with mostly facultative myiases seen. The patients are often debilitated, of lower economic status, homeless, or substance abusers.
- bedside USS may diagnosis an abscess or larval FB
- human bot fly - mainly tropical Western Hemisphere such as Central and Sth America
- Tumbu Fly - mainly Africa
- Lund's fly C. rodhaini - mainly tropical Africa
- screw fly - usual mammal is goat, thuis in humans mainly affects wounds eg. Colombia
- reindeer warble fly in Scandinavia
- Wohlfahrtia magnifica Eurasia and Nth Africa and may cause Schineria sp. bacteraemia 9)
hornets, bees and wasps
- Japanese giant hornet
- can grow to 4cm long with a wingspan of 6cm
- African killer bees
- dangerous mainly due to their numbers and propensity to chase and sting those who provoke them - especially targeting eyes
- these generally are mainly a nuisance causing painful stings but may cause anaphylaxis
- driver ants - a large genus of army ants found primarily in central and east Africa, although the range also extends to southern Africa and tropical Asia. Have powerful jaws (these have been used as emergency sutures) which can cause significant wounds, and can sting but rarely do so.
- fire ants - red stinging ants which are invading other countries such as USA, Brisbane in Australia
- bullet ants - known for their very painful sting which can last 24hrs - humid lowland rainforests from Nicaragua and the extreme east of Honduras and south to Paraguay
insect_bites.txt · Last modified: 2022/12/28 01:54 by wh