Arthropod Parasites: Flies & Myiasis Spencer Greenwood Dept. of Biomedical Sciences Office: 3313 N AVC North Annex 566-6002 (W) 892-4686 (H) Sgreenwood@upei.ca
The Flies - Diptera P Over 120,000 described species P The flies of veterinary importance are Ectoparasites as adults or as larvae Rarely ectoparasites in both stages
General characteristics
General characteristics Head & Mouthparts
Pathology Biting Flies P 50% of the annual losses in cattle production from all livestock pests in USA P Blood feeders puncture skin directly Pain & allergic reactions to saliva P Acute blood loss Livestock have been killed by swarms of biting flies P Biological or mechanical vector http://www.shelbyvilledailyunion.com/features/images_sizedimage_163101916/r esources_photoview http://www.fathom.com/feature/190259/3747_insect5.jpg
Non-biting Flies P Feed on secretions or scavenge at wounds or body orifices P Annoy & disturb host Pathology P Mechanical vectors for many pathogens
Pathology Myiasis Flies P Lay eggs on tissues or in wounds of the host P Larvae invade tissues & can cause significant damage to the host
P All flies can cause considerable disturbance to the host Biting flies & Myiasis flies Dramatic escape responses resulting in self-injury Gadding P Large populations of flies can also cause death by suffocation after inhalation
Keds - Family Hippoboscidae Pages 58-59 P Melophagus ovinus is a wingless, blood-sucking continuous ectoparasite of sheep & goats http://www.flickr.com/photos/peteredin/2110659343/
Morphology P Brown in colour, 5-8 mm in length & dorsoventrally flattened P Wingless & fly- or tick-like in appearance with strong claws to help them cling to wool or hair
Life History P Female deposits 1 fully developed larvae at a time Egg hatches inside body & is nourished through 3 larval stages P Once deposited, larva immediately pupates Female glues it to wool! Emerges as an adult in 19-24 days
P Adult females live 4 months Produce 12-15 larvae P Transmission by direct contact Ewe to lamb is important P Survive up to 4 days off the host
Pathology P Cause irritation to skin making sheep restless so they do not feed well & may lose condition P Wool loss & discolouration (from blood) results in wool being downgraded Jean-Luc Cornec s telephone sheep from the Museum of Telecommunication in Frankfurt.
Control P Insecticides Dips/baths Dust/powders Spot-ons Sprays P Ivermectin? P Shearing can reduce numbers Treat with insecticides post shearing in warmer weather (Spring?)
P Infestation of the tissues or organs of animals by the larval stages of dipterous flies P Fly larvae feed directly on necrotic or living tissue of the host P Classification: Obligatory Facultative Accidental Myiasis Pages 59-66
Obligatory myiasis P A living host is required to complete development Will not survive without a living host Example Oestrus ovis
Facultative myiasis P Living host tissue is not required to complete development Example Lucilla spp.
Accidental myiasis P Rare chance events of myiasis i.e. accidental ingestion of fly eggs
Morphology of the larvae Cyclorrhaphous dipteran larvae
Morphology of the larvae Cyclorrhaphous dipteran larvae
Life History P Eggs deposited directly on an animal or on vegetation where they are likely to be picked up by a passing host P Eggs usually hatch within 24 hours & 3 larval stages follow in which feeding occurs P After the 3rd stage larva completes its feeding it leaves the host & finds a suitable place to pupate usually burrows into the ground P After pupation, adults emerge & may or may not feed before mating & depositing eggs
Pathology P Depends on - species of fly, number of larvae & site of infestation P Clinical signs: Irritation, discomfort, pruritus, weight loss, reduced fertility P Heavy infestations = severe tissue damage, hemorrhage, anaphylaxis, toxemia, secondary bacterial infections & death will result if not treated Cochliomyia hominivorax New World screw-worm
P Traumatic Myiasis Involves open wounds P Furuncular Myiasis Involves boil-like lesions P Creeping Myiasis Path of the larva can be traced beneath the skin P Sanguinivorous Myiasis A rare blood-sucking form
P Family Oestridae All obligate parasites & highly host specific Larvae have posterior spiracular plates containing numerous small pores (used for identification) Adults have primitive or non-functional mouthparts & are shortlived Bots & Warbles Family Oestridae
P Genus contains 5 species Oestrus P The Sheep Nasal Bot Fly - Oestrus ovis Important in North America
P Adults Grey 10-12 mm in length Small black spots on the abdomen Reduced (knob-like) mouthparts Morphology
Morphology P Immature larvae White ~1 mm P Mature larvae yellow or brown ~20 mm
Life History
Behavioural changes... P Larvaepositing females cause annoyance Sheep will run in panic Less grazing time & reduced weight gain...less wool!
Behavioural changes... P Sheep bunch together with heads towards the centre... Sheep meeting?
Pathology P Irritation & inflammation caused by the larvae can result in sticky mucoid nasal discharge, sneezing, nose rubbing or head shaking P Secondary bacterial infections
Treatment Ivermectin works for all stages
FYI...and it can happen to humans by sheep kissing
Gasterophilus P Obligate parasites of horses & donkeys: Gasterophilus nasalis Throat Bot fly Gasterophilus intestinalis Horse Bot Fly Gasterophilus hemorrhoidalis Nose Bot Fly Important in North America
P Adults 11-15 mm Resemble a Honey bee with a long curved ovipositor Non-functional mouthparts Morphology
1st stage larvae develop in mouth & moult to 2nd stage larvae which enters stomach Life History 3rd stage larvae develop in stomach for ~ 12 months Throat Bot fly - Gasterophilus nasalis = intermanibular region Horse Bot Fly - Gasterophilus intestinalis = forelegs Nose Bot Fly - Gasterophilus hemorrhoidalis = lips
Pathology P Light infestations have little effect P Larvae migration can cause irritation P Secondary bacterial infections P Pus pockets in the mouth P Oral lesions
P Larvae cause a chronic gastritis when attached to the stomach or intestine, Little evidence that this results in clinical disease P Bots may be associated with reduced weight gain, disruption of digestion, ulceration & stomach rupture
FYI P Humans may become infested with larvae Migrate through oral tissues but do not complete the life cycle Transmission by "horse kissing"
Treatment & Control P Washing legs with warm water will induce hatching of G. intestinalis & wash away the larvae P Topical treatments of pesticides to kill eggs/larvae
Treatment & Control P Traditionally, systemic pesticides to kill larvae Periodically throughout the season Final application 1 month before killing frost P Common treatments now macrolides Ivermectin, moxidectin
Hypoderma Warbles, Heel flies or Cattle grubs P Hypoderma lineatum Common Cattle Grub Occurs in USA & parts of Canada P Hypoderma bovis Northern Cattle Grub Occurs in Northern USA & Canada
P Adults 13-15 mm Bee-like appearance Lack mouthparts Morphology
Life History Migration: - 2-4 months : - Hypoderma lineatum - tissue around esophagus - Hypoderma bovis -tissue around spine - develop for ~3 months, then migrate to dorsal subq - final 2 moults in dorsal subq then exit host & pupate in soil
Pathology P Ovipositing females result in dramatic avoidance behaviour in cattle called "gadding" which can result in self injury, decreased time feeding... P Anaphylactic shock can result from warble being crushed during removal
P Warbles result in carcasses being trimmed & downgraded P Damage to the hides limits their value as leather
Treatment P After adult fly activity ceases & before larvae reach sensitive tissues Correct time varies with geographic region P If you treat when larvae are around esophagus & spinal cord Serious tissue & nerve damage Bloat, ataxia or paralysis P Systemic treatments Ivermectin, doramectin, moxidectin Organophosphates kill larvae early in migration
Treatment & Control P Manual removal of grubs < Inject 1 ml of 3% H2O2 into air hole & grub will emerge in ~ 15 seconds < Piercing grub during procedure can result in fatal anaphylactic shock!!!
Cuterebra spp. P Rodent or Rabbit Bot Fly Occasionally infests cats & dogs
Morphology P Adults Rarely seen Resemble a Bumble bee with vestigial mouthparts
Life History P Flies lay eggs along a rabbit run or near burrow P Eggs hatch instantly when animals run by & larvae attach P Larvae enter host through natural body openings & migrate through the tissues to species specific areas http://images.google.ca/imgres?imgurl=http://blog.rabbitnet
P Mature larvae leave skin & pupate in the soil http://images.google.ca/imgres?imgurl=http://farm1.static.flickr.com/
P Cats & dogs are infested when trying to stick their heads down a rabbit burrow entrance August - October
Pathology P Warbles cervical subcutaneous connective tissues in cats & dogs P Rarely, larvae may migrate into other tissues with fatal results if the brain is involved
Treatment P Surgical removal of the bot & wound treatment Often misdiagnosed as a tumour
FINAL LAB EXAM April 21, 2011 at 1300H in Laboratory 215N P Comprehensive - All Laboratories P Microscope or material at stations P 1 hour P 32 Questions 15 - Helminth section (Cawthorn) 15 - Protozoa transmitted by Arthropods & Arthropod Parasites (Greenwood) 2 - Aquatic parasitology (Cawthorn)
FINAL LECTURE EXAM P Format: 10 Multiple choice, 5 short answer 3 short to long answer (flea) 1 hour (50 marks from lectures 21-25) April 21, 2011 after Lab Exam Lecture Theatres A/B P Protozoa transmitted by Arthropods vectors Pages 1-13 P Veterinary Ectoparasitology Ticks: Pages 19-27 Mites: 28-36 Lice: 39-top of 41 Fleas: 44-49 Flies: 58-top of 65 (from Keds to Cuterebra) P Aquatic Parasitology - Dr. Cawthorn (10 marks)
Review session April 13th ~1600H Should improve chances of passing Exam! AVC VPM-122 EXAM REVIEW Don t Delay Study TODAY! 2011 April 13, 2011 By S. J. Greenwood PhD, DVM