Sydney University Department of Medical Entomology Westmead Hospital

 

Travel Bugs

Vector-Borne
Diseases

 

THE VECTOR THE DISEASE
ASSASSIN BUGS Chagas' Disease.
BODY LICE Epidemic Typhus.
FLEAS Plague; Murine Typhus; Tungiasis.
FLIES
(Non mosquito)
African Trypanosomiasis; Bartonellosis; Leishmaniasis; Loaiasis; Myiasis Flies; Onchocerciasis; Phlebotomus Fevers.
MITES Scrub Typhus.
MOSQUITOES
(Viruses)
Chikungunya virus; Dengue; Eastern Equine Encephalitis; Japanese Encephalitis virus; Mayaro virus; Murray Valley Encephalitis and Kunjin; O'Nyong-nyong virus; Oropouche Fever; Rift Valley Fever; Rocio Encephalitis; Ross River and Barmah Forest virus; Sindbis and Ockelbo virus; St Louis Encephalitis; Venezuelan Equine Encephalitis; West Nile Fever; Western Equine Encephalitis; Yellow Fever.
MOSQUITOES
(Other)
Malaria; Lymphatic Filariasis. 
TICKS (Bacteria) Lyme Disease; Tickborne Relapsing Fever; Tularaemia. 
TICKS (Protozoa) Human Babesiosis. 
TICKS
(Rickettsia)
Boutonneuse Fever; Human Ehrlichiosis; Queensland Tick Typhus and Flinders Island Spotted Fever; Rocky Mountain Spotted Fever; Siberian Tick Typhus.
TICKS
(Viruses)
Colorado Tick Fever; Crimean-Congo Haemorrhagic Fever; Issyk-Kul Fever; Kyasanur Forest Disease and Omsk Haemorrhagic Fever; Powassan Encephalitis; Tickborne Encephalitis. 
TICKS (Other) Tick Paralysis. 

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ASSASSIN BUGS

Chagas' Disease; caused by a trypanosome (Trypanosoma cruzi) and transmitted by blood sucking insects (Assassin bugs) belonging to the order Hemiptera. The disease tends to be associated with poverty. Symptoms in the chronic phase may include myocarditis (which can lead to death), and dilation of the oesophagus or colon. Chagas' disease occurs in southern and Central America.
 

BODY LICE

Epidemic Typhus; one of the most important diseases of humankind, which has caused mortalities of 30-60%, with around 30 million cases occurring around the time of the First World War. It is a severe disease, caused by the Rickettsia, R.prowazekii, and transmitted through the faeces of body lice. Signs of disease include a high fever, rash and thrombosis of peripheral blood vessels, which may lead to gangrene. It is a declining disease and once was widespread, it now occurs in Mexico, Central America, China, Africa and some Himalayan countries.
 

FLEAS

Plague; a bacterial infection (Yersinia pestis) spread by fleas from various species of rats. In the past, massive pandemics (worldwide disease outbreaks) have caused huge mortality, in one outbreak, a third of the human population died. The disease has various forms, the most common being bubonic plague, with features including fever, headache and painful swellings in the lymph nodes (called buboes). The disease is now treatable with antibiotics and a vaccine is available. It was distributed worldwide but is now only in parts of North and South America, Mongolia, China, Russia, Africa, India and Southeast Asia.

Murine Typhus; an infection caused by the rickettsia, R.typhi, and transmitted by rat fleas such as Xenopsylla cheopis. Causes a serious debilitating illness with fever that can be fatal, but is readily treatable. Once more widely distributed, it now occurs in India, Pakistan, and parts of Southeast Asia and USA

Tungiasis; caused by the chigger flea, Tunga penetrans, whereby considerable disability can occur as a result of the female of the species burrowing into the skin of the feet. The flea then feeds beneath the epidermis and cause severe irritation and inflammation, and secondary bacterial infections may result. The fleas are removed via surgery. T.penetrans occurs through many tropical and subtropical countries of South and Central America, and Africa.
 

FLIES - Non-mosquito

African Trypanosomiasis; results from an infection with a protozoan pathogen (Trypanosoma) transmitted by Tsetse flies (Glossina spp.) and produces the clinical syndrome known as "Sleeping Sickness". The disease begins with an ulcer (chancre) at the bite site, the trypanosome then invades the central nervous system and produces increasing indifference, lassitude and daytime sleepiness, and later death may result. Occurs through central and western Africa.

Bartonellosis; transmitted to humans by flies in the genus Lutzomyia and caused by the bacteria Bartonella bacilliformes. Causes a progressive anaemia with high mortality, or benign cutaneous eruptions. The disease is endemic in mountain valleys in the Andes of South America.

Leishmaniasis; a protozoan disease caused by infection with Leishmania and transmitted by flies of the genus Phlebotomus. The disease occurs in three forms; Visceral - which causes weight loss, anaemia and death if untreated; and Cutaneous and Mucocutaneous - results in nodular and ulcerative skin lesions, and can also be fatal (although less likely that the visceral form). Occurs in Africa, South and Central America, southern Europe and India.

Loaiasis; a nematode worm (Loa Loa), which is transmitted by the bite of tabanid flies. The worms move through connective tissue and tend to cause minimal local reaction, however they can move under the conjunctiva of the eye resulting in blurred vision and considerable pain. Occurs in tropical central Africa.

Myiasis flies; these are flies that parasitises either dead or living flesh. It is those species that invade living tissue, which cause the major problems. The flies can cause extensive destruction of flesh, particularly in the facial region, severe pain, and secondary bacterial infections can occur. The two main species responsible are Cordylobia anthropophaga from Africa and Dermatobia hominis from South America, although other species of flies can cause Myiasis.

Onchocerciasis; or "River Blindness" is caused by a filarial worm (Onchocerca) and transmitted to humans by blackflies of the genus Simulium. Initial disease starts with an irritating dermatitis (caused by the presence of the worms in the skin), subcutaneous nodules and lesions of the eye, which are formed as a result of the worm dying in the eye. This latter symptom can result in blindness. Occurs in central Africa, Central and South America.

Phlebotomus Fevers; many known viruses are responsible for what is called "Phlebotomus Fevers", which are transmitted by Phlebotomus flies. Symptoms include a sudden fever, headache, muscle pain, photophobia and a generalised feeling of weakness. Known from the Middle East, the Americas, Europe, Russia and Africa. Disease incidence varies from country to country.
 

MITES

Scrub Typhus; a rickettsial disease carried by several species of mites of the genus Leptotrombidium. Symptoms include an ulcer-like formation (called an eschar) at the bite site, fever, headache and rash. If left untreated, there is a 30% chance of fatality, although it is readily cured with antibiotics. Occurs in Southeast Asia, Siberia, India, New Guinea, Australia and Japan.
 

MOSQUITOES - Viruses

Chikungunya virus; an illness which includes fevers, nausea, vomiting, chills, rash, photophobia and joint pain. Generally the illness is short term and over within seven days, although the joint pain may last for many months in a few individuals. The disease occurs through Africa, India and Southeast Asia, generally from May to July.

Dengue; Dengue is the most important viral disease transmitted by mosquitoes afflicting humans in a world context. Clinical symptoms range from mild fevers, violent headache, severe pains in the muscles and joints, to a potentially life threatening haemorrhagic disease. Occurs in most tropical regions including Southeast Asia, Australia, Central America, North America, South America, India and Africa. (For more information see "Dengue" Fact Sheet).

Eastern Equine Encephalitis; an uncommon viral disease producing malaise, muscle and joint pain, chills, fever, and encephalitis which can be fatal. Infections occur mainly between May and August, mostly in the US and also Canada.

Japanese Encephalitis virus; one of the most important mosquito transmitted viruses worldwide, with up to 50,000 cases per year and a high fatality rate of around 25%. Disease is manifested by fever, headache, stupor, motor seizures and encephalitis. A vaccine is available. Known from southeast Asia, China, Japan, India, Korea and was recently introduced into the Torres Strait Islands of far north Australia. (For more information see "Japanese Encephalitis" Fact Sheet).

Mayaro virus; disease is shown by fever, headache, backache, chills, nausea, rash, muscle pain and joint pain. The disease has been recorded from South America and the West Indies and the virus has been recorded infecting humans in Central America. Epidemics occur during and around the rainy season.

Murray Valley Encephalitis and Kunjin; these viruses cause what is collectively known as "Australian Encephalitis". Disease is characterised by fever, anorexia, headache, nausea, vomiting, diarrhoea, and brain dysfunction including lethargy, drowsiness, confusion, ataxia and fits. A stiff neck can occur and encephalitis which can be fatal, although Kunjin appears not to cause fatalities. Known from Australia and New Guinea and generally occurs through the first four months of the year. (For more information see "Murray Valley Encephalitis virus and Kunjin virus" Fact Sheet).

O'Nyong-nyong virus; O'Nyong-nyong is a native African term descriptive of the disease and means "very painful and weak". The disease causes fever, rigors, headache, rash, and severe joint pain, which can be very debilitating. Only known from Africa and tends to be more common when the vectors are in large numbers following seasonal rains.

Oropouche Fever; generally causes fever, headaches, muscle and joint pain, chills, dizziness and photophobia, and occasionally results in nausea, vomiting and diarrhoea. Occurs through the rainy seasons of January to June mainly in Brazil.

Rift Valley Fever; causes high mortality in domestic animals but humans can become infected during epidemics. The disease causes fever, severe muscle pain (especially in the lower back), head, anorexia, and permanent damage to eyesight may result. Haemorrhagic manifestations can lead to fatalities. Outbreaks tend to follow heavy rains. Only occurs in Africa.

Rocio Encephalitis; principle symptoms include headache, fever, vomiting, malaise, anorexia, encephalitis and a variety of other neurological complaints. Fatalities have resulted. Epidemics peak from March to May. The disease occurs in southern Brazil.

Ross River and Barmah Forest virus; both produce a disease traditionally known as "Epidemic Polyarthritis". Symptoms include rash and mild illness with fever, to polyarthritis affecting chiefly the ankles, fingers, knees, and wrists. The disease occurs in Australia and mostly peaks in the first three months of the year. Outbreaks have occurred in the western Pacific Islands. (For more information see "Ross River and Barmah Forest" Fact Sheet).

Sindbis and Ockelbo virus; produces fevers, headaches, general weakness, rash and joint pain. Very widespread and occurs in most continents, although disease from Sindbis is rare in Australia.

St Louis Encephalitis; known to cause fatalities and principally affects the nervous system. Headaches, fever, nausea, weakness initially occur which later may develop into neurological symptoms. The disease mainly occurs in the US, peaking through the months from June to October.

Venezuelan Equine Encephalitis; first recognised in horses, this disease in humans produces flu-like symptoms with fever, malaise, chills, headaches, muscle and joint pains, plus neurological complications, which can result in death. Occurs in southern and Central America.

West Nile Fever; disease in humans is usually mild, with fever, weakness, headache, and muscle pain. Activity is mostly confined to the summer months and occurs in Africa, Europe, the Middle East and the former USSR.

Western Equine Encephalitis; important disease of horses with a high fatality rate. In humans the disease causes fever, chills, headache, nausea, vomiting, lethargy, stiff neck, meningitis and encephalitis. Fatality rates in humans vary from 3-15%. Occurs in the western areas of North America and also in South America, generally midsummer.

Yellow Fever; one of the earliest recognised mosquito-transmitted diseases that has caused massive epidemics with many thousands of deaths. Initial symptoms include weakness, muscle pain, headache and nausea, which can later develop into dehydration, jaundice, haemorrhages, tachycardia, and death can follow. A vaccine is available. The disease occurs in the tropical regions of Africa, and Central and South America, although it was once more widespread. Peak incidence is during the rainy season.
 

MOSQUITOES - Other

Malaria; this disease results from infection with a protozoan blood parasite transmitted by various species of mosquitoes belonging to the genus Anopheles. The disease causes fever (usually periodic), varying degrees of anaemia and splenic enlargement, and a range of syndromes resulting from the physiological and pathological involvement of certain organs, including the brain, liver and the kidneys. The infection often can be fatal in the absence of treatment. Currently it occurs in most tropical regions, although it was once more widely distributed. (See "Malaria" Fact Sheet for more information).

Lymphatic Filariasis; caused by nematode worms which block lymphatic vessels and produce the condition known as "Elephantiasis" (a gross swelling, usually in the legs and scrotum). Initial symptoms include fever and inflammation of the lymphatic vessels, which can later develop into irreversible elephantiasis. There are three types of nematodes that can cause the condition, although Wuchereria bancrofti is the most widely distributed. The disease occurs in most tropical countries.
 

TICKS - Bacteria

Lyme disease; caused by the spirochaete bacteria formerly known as Borrelia burgdorferi. Symptoms are wide ranging and include rashes, fevers, myalgia, arthralgia, and arthritis if let untreated. It is non-fatal and treatable with antibiotics. Lyme disease is the most commonly reported tick borne disease in the world. It is confined to the Northern Hemisphere and is particularly prevalent in northeast USA. Peaks in June and July. (For more information see "Lyme Disease" Fact Sheet).

Tickborne Relapsing Fever; caused by Borreliae spirochaetes and transmitted by soft ticks. The disease produces relapsing fevers, initially occurring around one week after the tick bite. Treatable with antibiotics. Occurs in most continents excluding Australia.

Tularaemia; a bacterial disease producing flu-like symptoms, with periodic severe fever, lesions at the bite site, conjunctivitis and swollen lymph nodes. Tends to occur through the summer months throughout Europe, Russia, Japan, Asia and North America.
 

TICKS - Protozoa

Human Babesiosis; similar to malaria in symptomatology with fevers, fatigue, chills, myalgia and anorexia. Occurs only in northeast USA and numbers of cases are low. Peaks in June/July.
 

TICKS - Rickettsia

Boutonneuse Fever; produces a mild to moderate fever, rash, and a lesion (or eschar) at the bite site. Is potentially fatal but treatable with antibiotics. Disease peaks through the warmer months. Present in Southern Europe, Africa and India.

Human Ehrlichiosis; a recently recognised disease which includes fever, headache, malaise, chills, sweating, muscle aches, nausea, and vomiting. The disease can be life threatening but is treatable with antibiotics, especially in the early stages of the disease. Occurs through the USA.

Queensland Tick Typhus and Flinders Island Spotted Fever; two similar rickettsia that cause comparable symptoms, including rash, an eschar at the bite site, headache, fever, flu-like symptoms and lymph node tenderness. Both diseases are not commonly reported and are confined to the east coast of Australia down into Tasmania (see "Spotted Fever" Fact Sheet for more information).

Rocky Mountain Spotted Fever; characterised by chills, fever and rash. May lead to convulsions, coma and death if untreated. Can be cured with antibiotics but still has a 5% fatality rate. Since 1984, the annual number of cases reported has been declining. Disease incidence peaks from April through to September. Occurs in USA, Canada, Mexico, Central and Southern America.

Siberian Tick Typhus; a spotted fever with rashes, headaches, fevers and is rarely fatal. Treatable with antibiotics. Occurs through Russia. Peaks during spring and summer.
 

TICKS - Viruses

Colorado Tick Fever; causes an acute febrile illness, sometimes with rashes. Can cause encephalitis in children. April to July is peak period of the disease. The disease is endemic in the mountainous states of western USA and Canada.

Crimean-Congo Haemorrhagic Fever; this disease can have extremely high fatality rates, up to 50%. The disease starts with flu-like symptoms such as fevers, malaise, headaches and muscles pain. This can later lead to vomiting, diarrhoea and rash. The disease is highly infectious and can be transmitted via contact with infected individuals. Cases generally occur through June to September. The countries of former USSR, Middle East, southwest Europe, Pakistan, South Africa and China are indigenous for the disease.

Issyk-Kul Fever; a rare viral disease from Russia which does not cause fatalities but produces fever, headache, dizziness, muscle pain, rash and nausea.

Kyasanur Forest Disease and Omsk Haemorrhagic Fever; these two viral diseases are closely related. Symptoms include headache, chills, fever, myalgia, diarrhoea, vomiting and bleeding. Fatality rates are around 10%. KFD is confined to western India while OHF occurs in west Siberia.

Powassan Encephalitis; an uncommon potentially fatal disease which can produce encephalitis. Symptoms include fever, convulsions, vomiting, respiratory difficulties and lethargy. Peak infection is from June to September and has been recorded from North America, Russia, China and Southeast Asia.

Tickborne Encephalitis; this disease still has around a 25% fatality rate. Initial symptoms include headaches, fevers and nausea, which may develop into paralysis, coma and death. Can be acquired from drinking infected milk. Incidence peaks in May and June. The disease is confined to western Europe and former USSR.
 

TICKS - Other

Tick Paralysis; appears to be caused by a toxin in the tick saliva. The initial symptoms may include unsteady gait, increased weakness of the limbs, multiple rash, headache, fever, flu like symptoms, tenderness of lymph nodes, and partial facial paralysis. Paralysis and death by respiratory failure can occur if the tick is not removed. Children are at greatest risk. Various tick species throughout the world can cause paralysis.
 

REFERENCES

Goddard, J. (1989). Ticks and Tickborne Diseases Affecting Military Personnel. USAF School of Aerospace Medicine, Texas.

Kettle, D.S. (1995). Medical and Veterinary Entomology. (2nd ed.). CAB International, Wallingford.

Monath, T.P. (1986). The Arboviruses: Epidemiology and Ecology. Vols. II-IV. CRC Press, Florida.

Peters, W. (1992). A Colour Atlas of Arthropods in Clinical Medicine. Wolfe, London.

<http://www.cdc.gov/travel/travel.html> Center for Disease Control Travel Information.

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