Difference between revisions of "Myiasis"

Revision as of 15:08, 7 June 2011

Also Known As – Fly-strike – Wound myiasis – Maggots – Strike – Fly infestation – Wool maggots

Cat with myiasis. Wikimedia Commons

Larval form of Gasterophilus spp stomach botfly. Wikimedia Commons

Caused By – Myiasis Producing Flies

Introduction

Myiasis is caused by infestation of live hosts with dipterous larvae.

Small and large ruminants and poultry can be affected.

These larvae then feed on the host’s living and dead tissue.

Myiasis Producing Flies can be obligate or facultative.

Myiasis Causing Flies

Obligate

Obligate flies occur exclusively in or on living vertebrates.

Oestrus ovis, Gasterophilus spp, Hypoderma spp, Dermatobia spp, Wohlfahrtia spp, Cochliomyia, Chrysomya bezziana and Cordylobia.

Facultative

Facultative flies are free-living and usually found in detritus or carrion.

Cochliomyia macellaria, Chrysomya megacephala, rufifacies and albiceps, Lucilla sericata and cuprina, Phormia spp, Protophormia spp and Caliphora spp.

For more information, see [Myiasis Producing Flies]]

Distribution

Myiasis Producing Flies are found in most regions of the world.

Signalment

Presence of wounds, wet fleece in sheep cases, recent surgery, bacterial wool/skin contamination and faecal contamination are the main predisposing factors for myiasis.

Density of stock will determine size and viability of the fly population.

Clinical Signs

Can be classified as cutaneous, nasopharyngeal, intestinal or urogenital.

Pain, Irritation, Discomfort, Alopecia and Pruritus locally.

Direct tissue damage, haemorrhage, hyperpigmentation and secondary infection.

Nasal myiasis causes irritation and epistaxis.

Aural myiasis can cause deafness, discharge and foul exudates.

Gastrointestinal myiasis often causes ulceration, GI bleeding, weight loss, diarrhoea and pupae are voided in faeces.

Warble flies cause cysts along the midline of the back.

Lucilia sericata tends to cause leions on the inner thighs and perineum due to faecal soiling.

Wohlfahrtia spp cause genital lesions on the vulva and prepuce.

Loss of feathers and soiling of the vent is seen in poultry.

In severe cases, anaemia, anaphylaxis and toxaemia may be fatal.

Reduced feeding and consequent weight loss and infertility.

Diagnosis

Diagnosis is primarily dependent on observation of larvae on the host or in the faeces.

Larvae may also be observed in the carcass at post-mortem.

Gastroscopy may be used in the case of gastric myiasis.

ELISA is also available for Hypoderma spp and Oestrus ovis.

PCR is available for Cochliomyia spp.

Treatment

Treatment with ectoparasiticides is usually effective.

Administration can be oral, topical or by subcutaneous injection and the type of myiasis should be considered when deciding upon route of administration.

Ivermectin and doramectin are both effective in the control of nasal myiasis , warble fly and Dermatobia when injected.

Moxidectin is the main drug for oral treatment. It is effective against Gasterophilus spp.

Topical treatment by pour-on or dipping is most effective against cutaneous/subcutaneous myiasis. A huge range of products are available. Resistance should be considered and monitored.

Control

Preventative treatment with ectoparasiticides is common.

Release of sterile insects is also possible and effective but expensive.

Vaccines are available against Hypoderma spp and Lucilia spp.

References

Animal Health & ProductIon Compendium, Myiasis datasheet, accessed 06/06/2011 @ http://www.cabi.org/ahpc/

@@ Line 1: / Line 1: @@
-*Infection by dipterous flies in moist body areas (''eg.'' perineum)
+Also Known As '''''– Fly-strike – Wound myiasis – Maggots – Strike – Fly infestation – Wool maggots'''''
-*Commonly affects sheep - [[Bacterial skin infections - Pathology#Ovine fleece rot|ovine fleece rot]]
-*Grossly:
-**Matted hair or wool, may be in wounds
-**Multiple holes or ulcers
-**Malodour
-*May result in death due to septicaemia or toxaemia
-*'''Cuterebra myiasis'''
-**Caused by ''Cuterebra'' sp
-**Young animals come into contact with eggs on stones or plants
-**Nodules with larvae in subcutis + respiration openings to surface
-*'''Hypoderma myiasis'''
-**Caused by ''Hypoderma lineatum'' or ''H. bovis''
-**Mainly affects cattle
-**Skin of legs is penetrated -> migration through [[Oesophagus - Anatomy & Physiology|oesophagus]] or vertebral canal to subcutis of back
-**Cause subcutaneous nodules with respiration openings
-**Larvae in cavity with fibrin and eosinophils surrounded by granulation tissue with eosinophil clusters
-*'''Screwworm myiasis'''
-**Occurs in Africa, Asia, Central and South America
-**Larvaae are deposited in wounds
-**Penetrate and liquify tissue
+[[File:Myiasis cat.jpg|thumb|200px|right|Cat with myiasis. Wikimedia Commons]]
-==Pathogenesis==
+[[File:Gasterophilus larvae.jpg|thumb|200px|right|Larval form of ''Gasterophilus spp'' stomach botfly. Wikimedia Commons]]
-*Production losses
-**Annoyance
-**Bites can lead to secondary infection by [[Myiasis Producing Flies|myiasis producing flies]] and other muscid species
-*Disease transmission
+Caused By – '''[[Myiasis Producing Flies]]'''
-**Pathogenic bacteria and viruses via mechanical transmission
-**Helminths can be introduced into the host
-***E.g. ''Stephanofiliaria'' a filarial nemadode found in the skin of cattle overseas
-==Haematobia irritans==
+==Introduction==
+Myiasis is caused by infestation of live hosts with '''[[Biting Flies | dipterous larvae]]'''.
+Small and large ruminants and poultry can be affected.
+These larvae then feed on the host’s living and dead tissue.
+[[Myiasis Producing Flies]] can be '''obligate or facultative'''.
+==Myiasis Causing Flies==
+===Obligate===
+'''Obligate flies''' occur exclusively '''in or on''' living vertebrates.
+''[[Oestrus ovis]], [[Gasterophilus spp]], [[Hypoderma spp]], [[Dermatobia hominis | Dermatobia spp]], [[Wohlfahrtia spp]], Cochliomyia, [[Chrysomya bezziana]] and Cordylobia.''
+===Facultative===
+'''Facultative''' flies are '''free-living''' and usually found in detritus or carrion.
+''Cochliomyia macellaria, Chrysomya megacephala, rufifacies'' and ''albiceps, Lucilla sericata and cuprina, Phormia spp, Protophormia spp'' and ''Caliphora spp.''
+For more information, see [Myiasis Producing Flies]]
+==Distribution==
+[[Myiasis Producing Flies]] are found in most regions of the world.
+==Signalment==
+Presence of '''wounds, wet fleece''' in sheep cases, recent '''surgery''', bacterial wool/skin contamination and '''faecal contamination''' are the main predisposing factors for myiasis.
+Density of stock will determine size and viability of the fly population.
+==Clinical Signs==
+Can be classified as '''cutaneous, nasopharyngeal, intestinal''' or '''urogenital'''.
+'''Pain, Irritation, Discomfort, Alopecia''' and '''Pruritus''' locally.
+'''Direct tissue damage, haemorrhage''', hyperpigmentation and secondary infection.
+[[Oestrus ovis | '''Nasal myiasis''']] causes irritation and [[Epistaxis | epistaxis]].
+'''Aural myiasis''' can cause deafness, discharge and foul exudates.
+[[Gasterophilus spp | '''Gastrointestinal myiasis''']] often causes '''ulceration, GI bleeding''', weight loss, [[Diarrohea | diarrhoea]] and pupae are voided in faeces.
+[[Hypoderma spp | '''Warble flies''']] cause '''cysts''' along the midline of the '''back'''.
+''Lucilia sericata'' tends to cause leions on the inner '''thighs and perineum''' due to faecal soiling.
+''[[Wohlfahrtia spp]]'' cause '''genital lesions''' on the vulva and prepuce.
+'''Loss of feathers''' and soiling of the vent is seen in '''poultry'''.
+In severe cases, anaemia, anaphylaxis and toxaemia may be fatal.
+Reduced feeding and consequent weight loss and infertility.
+==Diagnosis==
+Diagnosis is primarily dependent on '''observation of larvae''' on the host or in the faeces.
+Larvae may also be observed in the carcass at '''post-mortem'''.
+Gastroscopy may be used in the case of [[Gasterophilus spp | gastric myiasis]].
+'''[[ELISA testing | ELISA]]''' is also available for ''[[Hypoderma spp]]'' and ''[[Oestrus ovis]]''.
+'''PCR''' is available for ''Cochliomyia spp''.
+==Treatment==
+Treatment with '''[[Ectoparisiticides | ectoparasiticides]]''' is usually effective.
+Administration can be '''oral, topical or by subcutaneous injection''' and the type of myiasis should be considered when deciding upon route of administration.
+'''Ivermectin''' and '''doramectin''' are both effective in the control of [[Oestrus ovis | nasal myiasis]] ,[[Hypoderma spp | warble fly]] and [[Dermatobia hominis | Dermatobia]] when '''injected'''.
+'''Moxidectin''' is the main drug for '''oral treatment'''. It is effective against [[Gasterophilus spp]].
+'''Topical treatment''' by '''pour-on or dipping''' is most effective against '''cutaneous/subcutaneous myiasis'''. A huge range of products are available. Resistance should be considered and monitored.
 ==Control==
-*Resident fly so easier to control than visiting flies as spends more time in contact with the host
+Preventative treatment with '''[[Ectoparasiticides | ectoparasiticides]]''' is common.
+Release of '''sterile insects''' is also possible and effective but expensive.
-*However, [[Ectoparasiticides|insecticide]] resistance can occur quicker
+'''Vaccines''' are available against ''[[Hypoderma spp]]'' and ''Lucilia spp.''
+==References==
+<references/>
+Animal Health & ProductIon Compendium, '''Myiasis datasheet''', accessed 06/06/2011 @ http://www.cabi.org/ahpc/
 [[Category:Integumentary System - Parasitic Infections]]
-[[Category:To_Do_-_Steph]]
+[[Category:To_Do_-_CABI review]]