'UITPEULOOG' Gedoelstia hassleri
By By Dr Mackie Hobson BSc(Agric),BVSc

Dr Mackie Hobson (SAMGA)

Gedoestia hassleri  is better known as ‘Uitpeuloog’ , ‘Ophthalmomyiasis’ or‘ gedoelstial myiasis’. Cases of Gedoelstia are rare but a suspected case has  been diagnosed in an outbreak in a flock of Angora goats in the Pearston district in March/April 2016. Angora goats are not preferred hosts.

The usual incidence is over the summer months October to May but larvae have been recovered throughout the year. Peak incidence of the disease is February to May.

Blue and black wildebeest are the preferred hosts of larvae of this fly but they also infest hartebeest, blesbuck , tsessebe, blesbok and bontebok. No clinical symptoms are usually detected in these hosts. With the increase in the number of game farms in the Eastern Cape outbreaks may become more common.

Flies belonging to this genus deposit  larvae on the cornea or conjunctiva of the eyes of their hosts from where they migrate either via the optic nerve tract or artery to the subdural cavity and dura mater, and then via foramina in the cribriform plate and other foramina to the nasal passages and paranasal sinuses. They use their mouth hooks and body spines as well as pulsatile body movements to reach their destination.  Larvae may vary in size from 0.8-5mm in the first stage to 31mm in length in the 3^rd stage.

They can however also migrate via the blood system from the eye to the heart and then back to the lungs, trachea and via the soft palate to the nasal passages where the moult to 2^nd stage larvae. The larvae can overwinter in the host so the larvae are not exposed to the harsh winter.

In preferred hosts there is little reaction but in abnormal hosts such as the Angora goat the life cycle cannot be completed and considerable pathology results from the migration of the larvae. The migratory routes are primarily intravascular but extravascular routes occur primarily along the optic nerve and other nerves of the head may be used.

Clinical signs:

Three main forms of the disease caused by Gedoelstia larvae have been recognised in domestic animals,

1. The ophthalmic form which is a specific oculovascular myiasis called bulging eye disease or "uitpeuloog".This ranges from a mild inflammation to a very severe exophthalmia with protrusion of the eyeball.
2. The encephalitic form results in a variety of nervous symptoms depending on the damage caused by migrating larvae.
3. The cardiac form can result in death due to heart failure.

Usually an outbreak occurs where a number of animals  infected. In the case of the flock of Angora goats 7 goats become infested in late March.

Signs reported in domestic stock have included:

• Intense ocular pain
• Blephrospasm (blinking of eyelid)
• Lacrimation (excess tear production)
• Periorbital swelling (swelling around eye)
• White flecks, larvae may be visible on the cornea with superficial ulceration and fluorescein uptake
• Frontal sinus may develop fistula (seen in this case)
• Exopthalmus (Uitpeuloog) Protrusion of the eyeball
• Secondary maggot infestation

This condition must not be confused with ‘infectious opthalmia’ ‘pink eye’ see https://www.angoras.co.za/page/opthalmia#120 or Nasal worm (Oestrus ovis) see https://www.angoras.co.za/page/nasalworm#141

Patholgy findings in the Angora goat suspected of having been infected by Gedoelstia.

(i) Macroscopically:

• Exopthamus of left eye
• fistula formation of frontal sinus which had become maggot infected.
• Inflammation and haemorrhage of duramater.

(ii) Microscopically (of samples analysed)

• Cerebrum: focal area of moderate haemorrhage
• Duramater: focus of macrophage infiltration in the dura with mild haemorrhage.
• Conjunctiva: Area of extensive severe inflammation with fibrin exudation. Marked granulation tissue development and neovascularisation and haemorrhage. Thrombosis and haemorrhage was also noted.
• Eye: neutrophilic exudation beneath the retinale vitreous contained homogenous eosinophilic material, neutrophils and haemorrhage.

Diagnosis: Panopthalmitis- suspected opthalmomyiasis

Treatment:

Goats should be removed from flock and isolated. Supportive treatment of shade, food and water must be provided.

• Spray the heads of Angora flock with a pyrethroid containing dip/spray to keep flies away and reduce the spread within the flock.
• Affected eyes can be treated with a cypermethrin spray which is effective in killing the larvae on the cornea and conjunctiva.
• Macrolytic lactones (ivermectin family) Closantel and rafoxinide containing drugs may help in the treatment. See https://www.angoras.co.za/page/anthelmintic_drug_list#38
• Topical eye treatments and pain relief will help with secondary pain, inflammation and infection.

REFERENCE

Parasites of domestic and wild animals in South Africa. XLVI. Oestrid fly larvae of sheep,goats, springbok and black wildebeest in the Eastern Cape Province.I.G. HORAK Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria

Ticks, mites and insects infesting domestic  animals in South Africa C.Howell, Jane Walker, E.Nevill

Zumpt 1965; Horak & Butt 1977b; Horak et al. 1983

Dr C Martin Idexx laboratory

Vetnuus February 2014

By Lo-An Odayar BVSc MMed Vet (Ophthal) JHB/Cape Animal Eye Hospital