Infectious Kerato Conjunctivitis

It is an infectious disease of cattle characterized by conjunctivitis, blepharospasms, lacrimation and varying degree of corneal opacity and ulceration.

Distribution

The disease is world wide in distribution. The disease has been recorded from various states in India. Mitter (1957) reported for the first time kerato-conjunctivitis in cattle from West Bengal. Ahmed and Rao (1956) reported the disease from Andhra Pradesh. Adinarayan and Singh (1961) reported the disease from Utter Pradesh. Mishra and Nayak (1966) reported the disease from Orissa. Knot and Ajinkya (1980) reported the disease from Mumbai. It is found to be more prevalent in herds where large number of animals are kept in confined areas.

Aetiology

The disease is caused by Moraxella bovis. It has been pointed out that a virus and rickettsia can cause similar condition. But, it is now emphasised that M. bovis is the true aetiological agent. M. bovis is gram negative, non-acid fast, pleomorphic coccobacillus with rounded ends, occurring in short chain. Non-motile, non-sporulating, metachromatic granules are noted in ageing culture. Colonies are firm to touch and break when handled with platinum loop. Both haemolytic and non-haemolytic types have been recorded. Association of infectious bovine rhinotracheitis, sunlight, wind, dust, flies and nutritional deficiencies have been found to exert effect on the disease processes.

Susceptible Hosts

Cattle are chiefly affected. Young calves are more susceptible. Previous infection appears to confer significant immunity which last through next session when further re-infection confer further immunity.

Seth and Chandrasekhara (1957) are of the opinion that the disease occur in all ages and breeds of cattle but Adinarayan and Singh (1961), remarked that adult suffers less than young ones because of immunity acquired through inapparent infections. The disease has also been recorded in buffalo and goat.

Mode of Transmission

The infection is transmitted by direct contact with ocular and nasal discharges or indirectly by mechanical contact with insect vectors. The isolation of organism from fly Musca domestica suggested that disease spreads through flied mechanically apart from direct contact. Mishra and Nayak (1966) mentioned that rainy seasons helps the spread due to favourable fly breeding in that season. Sinha (1979) remarked that disease spread to a great extent during warmer months. Trauma due to awn and other ways as well as other eye diseases help in transmission. Experimental transmission in cow and buffalo calves has been possible.

Pathogenesis

In natural cases, the organisms are localized in one or both the eyes. The organisms do not reach the blood stream. There is initial conjunctivitis and then keratitis. The cornea loose its transparency due to oedema. There is growth of blood vessels and appearance of fibroblasts.

A dermo-necrotic endotoxin has been suggested which is responsible for causing lesions in calves.

Clinical Findings

Four clinical stages of the disease have been ascribed.

1st Stage: There is tearing from the affected eyes.

2nd Stage: There is ulceration with dropping of eyelids.

3rd Stage: There is vascularization and repair of cornea.

4th Stage: There is healing and formation of scar tissues.

There is an incubation period of 2-3 days. The signs are more severe in young ones than adult cattle or buffalo. There is profuse watery lacrimation accompanied by thick eye discharges at the canthus within 24 hours. A clear line on the face below the inner canthus of the eyes with severe conjunctivitis, profuse watery or mucopurulent eye discharges. This is followed by photophobia, bleb formation, swelling of the eyelids, matting of eye lashes with smoky or diffuse corneal opacity. There is central or marginal keratitis and corneal ulceration. Very severe keratitis and corneal ulceration involving whole cornea and complete blindness is not uncommon in goats.

Acute, sub-acute and chronic form of the disease have been described. Acute form of the disease is characterized by lacrimal discharge, severe conjunctivitis, keratitis, diffused and net work of blood vessels are fully engorged. In chronic form, the lacrimal discharge is viscid and there is hypertrophy of conjunctiva accompanied by keratitis, diffused corneal opacity and occasional ulcer.

In lactating animals, the milk yield may drop considerably over a period of two to three months. The working capability of bullock may be reduced.

The foul smelling discharge attract large number of flies and they harbour around the eyes. In order to expel them, the animal constantly shake its head. Due to severe photophobia, the animals run to have shelter under trees and shades.

The matting of hairs over the skin on the cheek due to constant flow of the lacrimal discharge give rise to dermatitis.

Diagnosis

It is based on the following:

(i) Characteristic clinical manifestations.

(ii) Sporadic occurrence of the disease.

(iii) Bacteriological culture of the organism.

The culture may be made as suggested Mishra and Nayak (1966).

The affected eyelids and surroundings should be cleaned with soap and water.
Discharge from inside of eyes should be irrigated with normal saline.
The materials from eyes should be collected by means of sterile platinum loop.
The material thus collected should be transmitted to blood agar slants and nutrient broth for growth.
The swabs may be streaked on freshly prepared blood agar plates.
The plates are to be incubated at 37° C for 24 hours.
The development of clear zone will indicate that the organisms are haemolytic in nature.

Serological Tests

Serum agglutination test: A titre of 1:80 to 1:64 are observed at 2-3 weeks following clinical signs.
Modified agar gel diffusion test: This test is performed to know the antibody changes.
Immunofluorescence test: It helps to locate the diplobacillus in eye secretions.

Differential Diagnosis

The disease has to be differentiated from the following diseases:

Traumatic conjunctivitis
Infectious bovine rhinotracheitis and keratitis due to bovine malignant catarrh. These have got clinical signs other than ocular manifestation.
Photosensitization keratitis
Eye worm. Presence of ocular nematodes.
Rickettsial conjunctivitis. Giemsa stained smear of eye discharge will reveal rickettsial organisms.
Mycoplasmal keratoconjunctivitis. This may occur in cattle as well as goats. M. mycoides sub spp. mycoides large colony has been isolated from goat in India. The goat may show signs of conjunctivitis followed by keratitis with blepharospasms, photophobia and epiphora. Conjunctivitis in sheep and goat in India should also be viewed from the perspective of mycoplasmal infection and treated accordingly.

Treatment

Treatment with ophthalmic ointment containing Chloramphenicol, Oxytetracycline, Penicillin, Streptomycin has been suggested.
Treatment with Tylosin has been recommended.
Argylol 25% and Protargol (10%) thrice daily for 7 days gives result.
Intramuscular injection of cortisone acetate (100 to 150 mg) in conjunction with local treatment with antibiotic ophthalmic preparation has been made successfully.
Subconjunctival injection of dexamethasone has been recommended.
Topical ophthalmic anaesthetic combined with atropine administration is indicated to minimize ciliary spasms and pain.
Blepharorrhapy has been advocated where third eye lid is temporary sutured across the globe of the eyes for several days to promote healing.
A modified membrana nictitans flap technique has been used successfully in the treatment of cattle with ulcerative keratitis. The flap is held in place for 7-10 days.

Control

It is not possible to eradicate the disease because of the method of spread.
It will be logical to keep the animals under proper surveillance in endemic zone.
Cattle showing excessive lacrimation should be isolated and treated.
Recovered cattle remain immune upto 12 months.
Vaccine, if available may be tried.
Vaccine prepared from M. bovis gives some amount of protection.