BLINDNESS or ‘Apparent Blindness’ in Angora Goats
By Dr Mackie Hobson BSc(Agric),BVSc

1. Disease Syndromes

Blindness or ‘apparent’ blindness in Angora goats can be caused by a number of factors and is often hard to diagnose.

Conditions affecting the ‘eye’ can be divided into the factors effecting the:

1. External eye ( eyelids, eyeball, conjunctiva and cornea)
2. Internal eye ( Uvea, lens and retina)
3. Nerve pathway and the brain - central nervous system (CNS)

1. Factors affecting the EXTERNAL EYE

1. Opthamnia ‘aansteeklikeblindheid’ ‘Pink eye’

This is probably the most common condition effecting the eye and sight of Angora goats. The proper name is ‘infectious keractoconjunctivitis’ which is the inflammation of the cornea and conjunctiva. Pink eye affects Angora goats and sheep. The bacteria implicated (Chlamydophila, Mycoplasma or Moroxella) cause the condition to be highly infectious and easily transmitted between infected goats. The Chlamydia organism is the same organism that can cause enzootic abortions in ewes.

The cornea (surface of the eyeball) may at first appear grey and turn blue/white. The eyelids may stick together and excess tear production occurs. The conjunctiva is red and inflamed.

An ulcer may develop on the cornea and the cornea may even rupture.

See: https://www.angoras.co.za/page/opthalmia#120

1. Trauma and abrasions to cornea

Any scratch or laceration by vegetation or any material may damage the cornea. The depth of injury may vary from a superficial ulcer to penetration of the cornea.

Corneal injuries are painful and the eye may be kept shut. Swelling and cloudiness of the eye can be seen.

1. Conjunctivitis

Conjunctivitis is the inflammation of the conjunctiva. This results in redness and discharge from the eye

Conjunctivitis can be caused by:

• Irritants (dust, wind)
• Bacterial infections (see ‘pink eye’ above)
• Trauma to the conjunctiva
• A result of other eye problems, entropion for example.

1. Grass seeds

It is not uncommon for goats to get grass seeds penetrating the tissue around the eye or damaging the cornea when grazing feed containing grass seeds. The eye becomes swollen, the conjunctiva is red and the cornea is usually blueish in colour (inflammation). The eye is usually held shut due to the discomfort of the grass seed.

1. Thlezia rhodesii (eye worm)

Eye worms (Thelazia rhodesii) are usually found in cattle but goats can be effected.

1. Entropion

Inversion of the lower eyelid is either present at birth or appears soon afterwards in kids. The ocular discharge quickly becomes purulent. Direct contact between the eyelashes and cornea causes a severe keratitis with ulceration in more advanced cases with consequent blindness. The condition frequently affects both eye. The condition may be inherited.

1. Periorbital eczema

Periorbital eczema can occur when trauma occurs to the skin around the eye such as at feeding troughs or thorn scratches. The trauma to skin allows entry of Staphylococcus aureus which causes a local infection. The eyelids can become swollen and block vision in that eye. As the area heals the hair is lost around in a 2cm margin around the eye.

1. Neoplasia (Cancer of the eyelids)

Cancer (squamous cell carcinoma) although more common on the ear of the Angora goat can occur on the eyelids.

2. Factors affecting the INTERNAL EYE

1. Glaucoma:

Glaucoma is caused by an abnormal increase in pressure inside the eyeball and leads to a swollen, large, protruding eye which may have a blueish colour. Glaucoma in Angora goats are usually caused by diseases causing inflammation to the eye such as ‘pink eye’, corneal ulcers, trauma or cancer.

The reason for the swollen globe is that the drainage of the fluid contained in the eye is impeded, fluid and pressure build in the eye which may lead to damage to the retina and optic nerve can result in permanent loss of vision. 

1. Anterior uveitis 

Signs of anterior uveitis may include pain, redness, excess tears, and closure of the eyelids. It may affect one or both eyes. Within two to three days, the surface of the eye develops a bluish-white opacity.

Causes include trauma, corneal ulcers, infections such as Mycoplasma and Listeria, Chlamydia and Toxoplasma

1. Cataracts

Cataracts are the loss of opacity of the lens. Angora goat kids may have cataracts at birth as they can be hereditary. Other factors can also cause cataracts to develop such as trauma to the eye or any inflammatory disease of the eye.

1. Retinal degeneration

This can be caused by any inflammatory condition such as trauma, infection, cancer and glaucoma. Malnutrition is also thought to play a role and it is thought the condition may be hereditary. Infections of Listeria, Toxoplasma, and the bluetongue virus can all cause inflammation and problems in the retina. Vaccinating ewes with a modified live bluetongue vaccine during the first half of gestation can also cause retinal damage to their kids. Deficiencies in vitamin A can also cause the retina to degenerate. Apart from being blind no other external sign is visible.

3. Factors affecting the Nerves and central Nervous System (CNS)

1. A direct physical disruption of the optic nerve or brain tissue can cause blindness.

 Examples include:

• an abscess
• growth (neoplasia)
• severe haemorrhage through trauma

1. Anthelmintic (worm) doses

Roundworm treatments containing Rafoxanide and Closantel (Group 4 and found in some combinations) can potentially cause blindness in Angora goats if overdosed.

Trials indicated that kids dosed at 4x the therapeutic dose went blind.

Kids not affected too badly recovered over 3-4 weeks

See: https://www.angoras.co.za/article/rafoxanide-and-closantel-toxicity#227

1. Birth defects

The use of live vaccines in pregnant ewes may cause blindness in kids

1. Vit A fefficiency

Vitamin A is synthesized from carotene, which is present in green plants, so levels will be determined by the veld condition and will be significantly lower in winter veld and in times of drought. B-carotene levels decrease in stored feeds over time.  Most of a dose of Vit A is excreted within a week and the remainder stored in the liver. These liver reserves may last for 6 months in the Angora goat.

B-carotene deficiencies occur during droughts, when lucern hay and concentrate diets are fed. The feeding a urea lick, deficiencies in P or Vit E prevents the transformation of B-carotene to Vit A. A high Ca and low Zn diet can also result in Vit A deficiency. Vit A is essential in production of progesterone so deficiencies result in poor expression of oestrus, delayed ovulation and birth defects and negatively affect immune status . Deficiencies can also result in eye disorders, blindness, increased respiratory disease and decreased mohair production.

1. Vit B1 (thiamine) deficiency

Polioencephalomalacia (PEM) - caused by Vit B1 (Thiamine) deficiency simply literally means softening of the brain. It is a disease that is seen more commonly in Angora kids grazing lucern lands or fed concentrates especially if containing molasses.

https://www.angoras.co.za/article/polioencephalomalacia-pem#217

1. Neurological form of enterotoxaemia ‘Pulpy Kidney’

The goats appear to have a depressed mental state, appear blind and may circle and be ataxic. See the SAMGA website https://www.angoras.co.za/article/clostrdium-perfringens-type-d#256

1. Plant poisoning

• Ornithogalum spp (Chinkerinchee poisoning)

No cases in Karoo

• Helichrysum argrosphaerum (‘Sewejaartjies’, Wild everlasting)

No cases in Karoo

1. Uitpeloog (Gedoelstia hassleri)

https://www.angoras.co.za/article/uitpeuloog-gedoelstia-hassleri#242

1. ‘Domsiekte’ Pregnancy toxaemia and hypoglyceamia

Apparent blindness observed https://www.angoras.co.za/article/domsiekte-ketosis-pregnancy-toxaemia#254

1. Rabies

Goats may appear blind, see SAMGA website https://www.angoras.co.za/page/rabies#109

1. Urea toxicity

Urea poisoning can occur when Angora goats take in excess amounts through a lick or if a lick gets wet (urea dissolves easily in water). Death and many other clinical signs can be seen. See SAMGA website https://www.angoras.co.za/article/urea-poisoning#247

1. Listeriosis

The brain form of Listeriosis where goats may appear blind, see SAMGA website https://www.angoras.co.za/article/listeriosis#255

REFERENCES

http://www.infovets.com

Prof. Gareth Bath, Fakulteit Veeartsenykunde, Universiteit van Pretoria