ent 392 - lecture 18 biting midges ; diptera - ceratopogonidae

Ceratopogonidae

 a cosmopolitan nematoceran family

 ~6200 extant described spp.

 many extinct ones known only from amber

Culicoides

 Several species of concern, but most are found in the genus Cu___

 Includes most animal disease vectors

 Wide range of geographic regions (including Canada)

biting midge

Many common names in addition to bit__midge:  e.g., no-see-ums, punkies, moose flies, sand flies (shared with phlebotomine & simuliid flies)

tiny ; setae

MORPHOLOGY

 Adults are very ti__ (1-2.5 mm)

 often go unseen despite painful bites

 Small head, large thorax

 wings often with characteristic patterns

 caused by clusters of se__

mandibles

MORPHOLOGY

 mouthparts in blood-feeding females extended in a beak-like fashion

 have blade-like ma____ with teeth at the tips

 maxillary palps with sensory pits for finding feeding sites

filiform ; plumose

 Female antennae are fili_

 Male antennae are plu__

anautogenous

LIFE CYCLE AND ECOLOGY

 Most species females are anau____

 require blood meal for 1st batch of egg

 a few spp. are autogenous

moist substrates

LIFE CYCLE AND ECOLOGY

 eggs laid in batches on moist _____

 depending on species could be in wet leaf litter, soil, manure, mosses, littoral and riparian zones

 Hatch after 2-7 days

instars ; cutaneous

LIFE CYCLE AND ECOLOGY

 larvae (4 ins___) live in aquatic/semiaquatic environment

 Use cut___ respiration

 depending on species, larvae can be predators, detritivores or microbivores

 Larval stage is 2 weeks to 1-2 years

multivoltine

LIFE CYCLE AND ECOLOGY

 pupation occurs near surface of substrate

 prothoracic horns connected to tracheal system penetrate water film for air

 can be mult___ if conditions suitable

 both males and females feed on plant sap and nectar

 primary energy sources for flight

 some spp. are important pollinators,

 Ex: cocoa plant

swarming

LIFE CYCLE AND ECOLOGY

 Mating usually involves swa___

 large aerial aggregation of males near potential breeding sites

 May also breed near hosts

 males recognize females based on wingbeat frequencies and sex pheromones

 antennae used to detect both

 male-female couple in midair, but copulation occurs on the ground

 Adults survive 2-7 weeks

protein ; generalists

LIFE CYCLE AND ECOLOGY

 Egg production requires a pro___ source,

 Species specific:

 Hemolymph or

 vertebrate blood

 male ceratopogonids do not feed on animal fluids

 vertebrate feeders vary in preferences

 some prefer mammals, birds, reptiles, or amphibians

 Some are gene____

leptoconops ; pharyngeal

LIFE CYCLE AND ECOLOGY

 Circadian patterns of biting activity depends on species. Ex:

 Culicoides (nighttime/crepuscular feeders)

 Lep_____ (daytime feeders)

 Also dependent on temperature, light intensity, relative humidity (prefer high RH) and wind

 weak fliers, deterred by winds > 9 km/h

 Pool feeders

 lacerate skin and capillaries with mandibles; blood pools

 blood is drawn into foregut via pha_____ pump

 after feeding, female retreats to shelter where she rests while eggs develop

Nematodes

MEDICAL IMPORTANCE

 Bite reactions

 annoying pests

 some people have very strong reactions to the saliva

 Transmission of disease-causing agents

 Viruses

 many, but only one of high medical concern

 Nema____

 Mansonellosis

bite ; papules ; sensitized

MEDICAL IMPORTANCE

Bi__ Reactions

 can cause intense pain and itching

 Leaves pa___ - discomfort can last from few minutes to hours

 or days for people who are sensi___ to the saliva

 scratching may lead to secondary infections

allergy ;immediate ; delayed

MEDICAL IMPORTANCE

 biting midge all___

 nearly 60% of exposed subjects develop reactions to midge bites

 two types of reactions:

 Imm__ : large local swelling at biting sites within one hour of the bite

 De___ : intense pruritis and weeping blisters at biting sites 6– 24 hours after the bites

viral ; reservoir ; monkeys

MEDICAL IMPORTANCE : OROPOUCHE FEVER

 Epidemiology is complicated

 multiple vir___ strains

 3 distinct genotypes (I, II, and III)

 Genotype I - most widespread in Brazil, also in Trinidad

 Genotype II - found in Brazil (Para state, Rondônia) and Peru

 Genotype III - reported only in Panama

 potential rese___ hosts unclear and possibly diverse

 mon___ , birds, sloths carnivores, domestic birds…

febrile ; photophobia ; recurrence

MEDICAL IMPORTANCE : OROPOUCHE FEVER

 causes a non-fatal, acute feb___ illness

 Incubation: 4-8 days

 Symptoms are similar to non-severe dengue fever (more on this later)

 headaches, dizziness, phot____

 general muscle and joint pains (2-5 days)

 can lead to prostration

 recur____ of symptoms can prolong illness  ~2 weeks

Serological

MEDICAL IMPORTANCE : OROPOUCHE FEVER

Diagnosis

 Symptoms

 Sero___ testing

vaccine

MEDICAL IMPORTANCE : OROPOUCHE FEVER

Treatment

 no vac____

 focuses on symptoms

 infections are usually self-limiting and complications are rare

 patients generally recover fully with no long term ill effects

 in sum, the most important ceratopogonid-borne virus isn’t all that bad

black flies

MEDICAL IMPORTANCE : MANSONELLOSIS

 Transmitted by Culicoides midges and bla__ fl___

 Caused by three species of filarial nematodes in the genus Mansonella

perstans ; streptocerca ; ozzardi

MEDICAL IMPORTANCE : MANSONELLOSIS

three species of filarial nematodes in the genus Mansonella:

 Mansonella pers___

 endemic throughout much of Africa & some neotropical regions of Central and South America

 was likely introduced with the slave trade

 M. strep___

 In tropical regions of West and Central Africa

 M. ozza___

 Central & South America

 Also on several Caribbean islands

focal ; juvenile ; cavities

MEDICAL IMPORTANCE : MANSONELLOSIS

 Transmission of Mansonella spp. tends to be highly fo___

 local prevalence varies widely within endemic regions

 travel-related cases are unusual but documented

 very tiny juv___ nematodes (microfilariae, ~200 um long and 5 um wide) travel in circulating blood of human host

 picked up by feeding Culicoides spp. and black flies

 Adults found in human body cavi___ or skin

 Location depends on species

 adult females range from 3-8 cm long

humans ; primates

MEDICAL IMPORTANCE : MANSONELLOSIS

• M. perstans appears to be solely hosted by hu____

• other two species can be hosted by non-human prim___

asymptomatic ; hyperpigmented ; lymphatic

MEDICAL IMPORTANCE : MANSONELLOSIS

 usually asym___ and regarded as non-pathogenic

 considered a minor filarial disease with very low mortality

 sometimes cause medical problems:

 joint pains, fever, fatigue, transient swelling, hives, and increased white blood cell counts

 hyper____ lesions on the torso are reported in association with M. streptocerca

 Severe cases can block/inflame lym___ vessels causing elephantiasis-like symptoms

ocular ; microfilariae

MEDICAL IMPORTANCE : MANSONELLOSIS

 oc___ problems

 when micro___ invade the conjunctiva or periorbital connective tissues in the eye

 swollen eyelids, excessive tear production, itching, proptosis (from bulbar conjunctival nodules)

samples ; biopsy ; PCR

MEDICAL IMPORTANCE : MANSONELLOSIS

 Diagnosis

 blood sam__ confirming microfilariae presence

 skin bio___ examination for microfilariae in the tissue

 P__ assay

ivermectin

MEDICAL IMPORTANCE : MANSONELLOSIS

 Treatment

 ive____ is effective against microfilariae

 Adults can be surgically removed

reactions

CERATOPOGONIDAE : VETERINARY IMPORTANCE

As etiological agents

 Biting midges cause annoyance to livestock

 Can cause skin rea___ (ex: equine allergic dermatitis)

vectors

CERATOPOGONIDAE : VETERINARY IMPORTANCE

As vec___

 only a few cause significant disease in horses, sheep, & cattle:

 Bluetongue (virus)

 Epizootic hemorrhagic disease (virus)  African horse sickness (virus)

 Haemoproteus meleagradis (blood protozoans)  Equine onchocerciasis (nematode)

hypersensitivity ; sensitization ; itching ; riding

VETERINARY IMPORTANCE : EQUINE ALLERGIC DERMATITIS

 This hyper___ is a hereditary trait

 horses may exhibit an allergic skin reaction to bites of ceratopogonids

 Reaction to salivary contents

 mostly prominent at withers, at base of mane and tail, ears

 caused by to salivary components

 normally develop sensi___ mall welts with little discomfort

 sensitized horses react with intense local inflammation and itch___

 irritable behavior, hair loss, skin blemishes, secondary infections

 affected animals unsuitable for ridi___

ruminants ; contagious

VETERINARY IMPORTANCE : BLUETOUNGE DISEASE

 Viral disease of rumi__ (sheep, goats, cattle, bison and deer)

 Non-conta___ ; only insect-borne

 First isolated in South Africa 1930s, now occurs in many parts of the world

sporadic ; epizootics

VETERINARY IMPORTANCE : BLUETOUNGE DISEASE

 spo____ occurrence

 typically only 1-2 individuals/herd exhibit symptoms

 epi_____ (animal epidemics) are rare

 E.g. Late 1950s: ~179,000 sheep killed in Spain & Portugal

 75% mortality

 Restrictions on exports can cost industries $millions

prevalence ; okanagan

VETERINARY IMPORTANCE : BLUETOUNGE DISEASE

 pre___ high (~20-50%) in US cattle

 Canada

 Occurred in the Oka__ Valley, BC *sporadic

 only cases outside of BC were in Ontario in 2015

 close (~100 km) to the U.S. border

 animals never left the farm of origin

Possible causes:

 ceratopogonids were blown over from the US

 Serious implications considering climate change

 Virus acquired from imported cattle that showed no symptoms

salivary glands ; temperature ; sexually

VETERINARY IMPORTANCE : BLUETOUNGE DISEASE

 Primary mode of transmission via infected Culicoides midges

 virus acquired when midge feeds on infected animal

 virus invades sal__ gla__ multiplies

 10-20 day incubation period; temp__ dependant

 transmitted to new host in saliva

 Culicoides vector remains infective throughout lifetime

 but no evidence of transovarial transmission

 Can also be sex___ transmitted via semen of infected rams and bulls

 currently no way to destroy the virus in semen of infected animals

 virus can survive indefinitely in frozen semen samples

serotypes ; geographic ; mortality

VETERINARY IMPORTANCE ; BLUETONGUE DISEASE

 Most animals remain asymptomatic

~ sources of infections

 ~25 ser___ , which vary significantly in their pathogenicity

~ multiple serotypes often occur within the same geo___ area

~ Some animals develop disease that worsens rapidly

~ mor___ usually within a week

~ long, slow recovery for survivors

mouth ; ulceration ; accumulation

VETERINARY IMPORTANCE ; BLUETONGUE DISEASE

 Symptoms in severe disease

~ lesions about the mou___ and muzzle

~ Swollen blueish/purple tongue

~ ulce___ and sloughing of skin tissues

~ inflammation & lesions between toes

~ respiratory difficulties due to fluid accu___ in lungs

~ internal haemorrhaging

 Death often caused by internal hemorrhaging or lung congestion

present ; PCR ; polyvalent

VETERINARY IMPORTANCE : BLUETONGUE DISEASE

Diagnosis

 Symptoms when pre___

 Otherwise:

~ P___ for viral RNA

~ Serological testing Treatment

 None available – can only treat symptoms

 polyvalent vaccines generally not effective

~ poly___ = single vaccine that immunizes against more than one strain of an antigen

~ Only serotype 10 currently has a functional vaccine

 Sheep that recover may exhibit natural immunity to the particular serotype

 Cattle do not develop immunity following infection

similar ; endemic ; deer

VETERINARY IMPORTANCE : EPIZOOTIC HEMORRHAGIC DISEASE

 Very sim__ to Bluetongue disease (also a virus)

~ but primarily affects wild ruminants

~ called Blacktongue disease in SE USA

 Transmitted by Culicoides spp. biting midges

 ende____ throughout USA & Western Canada

 Most important infectious disease in wild US de___ populations

~ causes sporadic die-offs in white-tailed deer,

~ Also effects pronghorn, bison, bighorn sheep, Rocky Mountain goats

 Cattle commonly exposed to EHD virus

~ Usually asymptomatic

equids ; elephants ; uncooked

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS

 Viral disease of wild and domestic equ___

~ zebras, horses, and mules

~ highly fatal in susceptible animals

~ donkeys are largely resistant

 other species show at most mild clinical signs

~ goats, sheep, domestic cattle, buffaloes, dromedaries, and ele___

 Transmitted by Culicoides spp.

~ May also be vectored by mosquitoes and camel ticks

 dogs believed to be important reservoirs in urban areas

~ consuming uncoo___ meat of infected horse carcasses

~ progression of disease in dogs is similar to pulmonary form in horses

Africa ; Middle

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS

 Prior to 1900s, African horse sickness was largely confined to South Af___

~ 1944 on: outbreaks among horses in several Midd___ East countries

~ E.g. 1959-1960: >300,000 horses died in the Middle East, Afghanistan, Pakistan, and India

pulmonary ; cardiac

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS

 Disease has four clinical forms

~ pul___ ~ cardiac ~mixed pulmonary-car___ ~ horse sickness fever

fatal ; sweating ; froth

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS
Pulmonary form

 Most fat__ (mortality up to 95%)

 Clinical symptoms develop within 3-5 days and is sudden

~ begin with fever followed by congestion of the mucous membranes of the eyes, nose, and mouth

~ profuse sweat__ , increased respiratory rates, fluid accumulation in lungs

~ fro__ from nostrils at terminal stage

~ death occurs within days

congestion ; subcutaneous ; death

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS

Cardiac form

 Mortality ~50%

 Clinical symptoms develop within 7-14 days

 Also begins with fever and con___ of the mucous membranes

~ extensive subcu____ edema visible in the neck and jugular area, in the muscles along the back and hips, around the eyes and eyelids, and in the jaws.

~ hemorrhages on the underside of the tongue

 deat__ usually occurs in 4-8 days

intermediate

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS

 mortality ~80%

~ inter___ between the pulmonary and cardiac forms

 characterized by clinical signs associated with each of the previous two syndromes

 death within 3-6 days

mildest ; appetite

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS

Horsesickness fever

 mild___ form of AHS

 animals usually recover following a low-grade fever, congested mucous membranes, loss of app___

 lasts ~1 week

serological ; vaccines ; immunity

VETERINARY IMPORTANCE : AFRICAN HORSE SICKNESS

Diagnosis

 sero___ testing

Treatment

 no cure for this disease

~ Only supportive therapy

 Annual vac___ effective in maintaining immunity

 In endemic areas, native animals may develop a natural or acquired imm___

~ introduced breeds/species are most susceptible

haemosporidians ; malarial

VETERINARY IMPORTANCE : BLOOD PROTISTS

 haemo___

~ blood parasites of reptiles, birds, and mammals

 related to mala___ parasites

 Transmitted by Culicoides spp.

 Three genera transmitted by biting midges

~ Haemoproteus

~ Hepatocystis

~ Leucocytozoon

 Complex malaria-like life cycle

~ will cover life cycle when we get to malaria

concern ; turkeys ; pathological ; infections

VETERINARY IMPORTANCE : BLOOD PROTISTS

 Haemoproteus meleagridis is main species of veterinary con___

~ primarily a parasite of wild and domestic turk___

 generally non-pathogenic, even in large numbers

~ birds usually exhibit few signs of stress or other patho___ effects

 But sometimes problematic in domestic turkeys

~ heavy infe___ can cause anemia, reduced weight gain and growth rates, inflammation of skeletal and cardiac muscles, lameness, damage to the spleen and liver, and a wasting condition associated with chronic infections

~ young birds are particularly vulnerable

horses ; different ; prevalence ; older

VETERINARY IMPORTANCE : EQUINE ONCHOCERCIASIS

 Caused by filarial nematode Onchocerca cervicalis

~ hor__ are only known hosts

~ diff__ species than human onchocerciasis (river blindness; O. volvulus)

 Occurs worldwide, but most problems reported in USA and Australia

~ prev___ high in USA (~85%)

~ usually in old___ horses

 Vectored by Culicoides variipenis

~ Black flies and other Culicoides spp. may also be vectors

EQUINE ONCHOCERCIASIS

VETERINARY IMPORTANCE : ____________

dermatitis ; inflammation

VETERINARY IMPORTANCE : EQUINE ONCHOCERCIASIS

 Causes der___

~ Microfilariae migration and aggregation causes inflammation and crusty dry patches that are irritating

~ infla___ can lead to hardened lumps

sensitized ; pruritis

VETERINARY IMPORTANCE : EQUINE ONCHOCERCIASIS

 sens___ horses develop various types of skin lesions

~ depigmentation, pru___ , scaling, and hair loss

~ on the face, chest, withers, and ventral midline where microfilariae most abundant

~ Seasonal migration of microfilariae lead to seasonal severity of symptoms

antihelminth ; effective

VETERINARY IMPORTANCE : EQUINE ONCHOCERCIASIS

Diagnosis

 Skin biopsy

 Positive response to antiworm treatment

Treatment

 anti___ drugs (e.g. ivermectin) are effective against larvae

~ Significant improvement within weeks of treatment

 No eff__ treatment against adult worms

~ Retreatment to manage recurring symptoms

reduce ; larvicides

BITING MIDGE PREVENTION AND CONTROL

Controlling midge population

 red__ availability of breeding sites

~ Proper irrigation and drainage

 Application of larvicides and adulticides

~ Adulticides as a fog during peak activity

~ larvi___ less successful

~ Breeding sites dispersed and hard to locate

garments

BITING MIDGE PREVENTION AND CONTROL

Individual protection of humans and animals: only effective approach

 Avoid outdoor activities during peak biting periods

 Insect repellents on exposed skin/animals and DEET-impregnated clothing

 Stable livestock at night

o Mostly effective if local midge species don't readily enter structures or if appropriate protective screening provided

 Horse gar___ can help protect sensitized horses