Content
Thelaziosis in cattle is a seasonal epizootic disease that is widespread everywhere. Characterized by inflammation of the conjunctiva and cornea of the eye. In the initial stages, thelaziosis is quite difficult to determine, since the clinical signs are mild. Advanced cases of the disease can lead to complete loss of vision and decreased animal productivity, so every cattle owner should know how the clinical signs of thelaziosis manifest themselves, as well as ways to prevent this disease.
Causes of thelaziosis and sources of infection
The causative agent of bovine thelaziosis is small nematodes belonging to the genus Thelazia. There are three types of biohelminths in cattle. Each of the nematodes parasitizes in different places:
- rhodesi is localized in the conjunctival cavity and under the third eyelid;
- gulosa, T. skrjabini - in the nasolacrimal canal and ducts of the lacrimal glands (sometimes in the conjunctival sac).
Cattle are infected with nematodes on pasture. In the spring, their females release first-stage larvae, which migrate with tears and mucus to the area of the inner corner of the eye, where they are swallowed by cow flies. In the body of the intermediate host, the larvae grow, go through two stages of molting, and after 2-4 weeks they turn into invasive larvae of the third stage.The latter move to the head part of the fly's body and through the proboscis enter the conjunctival sac of the animal's eye. After 1-1.5 months, the larva turns into a sexually mature individual. Adult nematodes can parasitize an animal’s body for up to a year, however, most often they die after 3-4 months.
Animals of all age groups are susceptible to thelaziosis. The disease is most acute in young cattle aged four months and older.
Nematodes are able to remain viable in winter. Their females, having overwintered in the eyes of sick animals, begin to lay eggs with the onset of summer flies. Thus, cattle affected by thelasia are the only source of infection in the spring.
Symptoms of thelaziosis in cattle
Thelaziosis in cattle occurs in three stages. Growing in the conjunctival area of the eyes, nematodes injure the delicate mucous membrane. Worms of the species T. rhodesi have chitinous spines on the front of the body, so this type of pathogen is considered the most dangerous.
At the initial stage of the disease the following is noted:
- conjunctival hyperemia;
- profuse lacrimation;
- photophobia.
It is quite difficult to recognize the symptoms of the disease at the first stage. The clearest clinical picture emerges after 2-3 days. The disease enters the second stage, which is characterized by the following clinical signs:
- purulent or purulent-serous discharge from the sore eye;
- copious mucous secretion;
- corneal clouding;
- swelling of the eyelid.
At the final stage of the disease, irreversible processes occur that can lead to blindness:
- the appearance of ulcerations on the cornea of the eye;
- soreness of the eyeball;
- increased body temperature;
- lack of appetite;
- depressed state.
At the third stage of the disease, milk production in cows decreases. Calves infected with biohelminths are retarded in growth and development.
Diagnosis of the disease
Diagnosis of thelaziosis in cattle is carried out according to the characteristics characteristic of this disease. To make a diagnosis at the first latent stage of thelaziosis, the conjunctival sac of a sick animal is washed with 50 ml of boric acid solution (3%). The resulting wash is collected in a container. Larvae and helminths can be seen with the naked eye or with a magnifying glass.
A laboratory study of tear fluid shows a decrease in the concentration of lysozyme. When diagnosing thelaziosis, epidemiological data and clinical signs are taken into account. In the absence of symptoms of the disease, for example, in winter, some types of helminths can be found in the nasolacrimal canal or excretory ducts of the lacrimal glands of an animal after slaughter. It is important to differentiate bovine thelaziosis from:
- herpes virus infections;
- moraxellosis;
- rickettsiosis.
Also, this disease must be differentiated from hypovitaminosis A.
Treatment of thelaziosis in cattle
For more effective treatment, the type of causative agent of thelaziosis is taken into account. For eye damage from T. gulosa and T. skrjabini, use a 25% aqueous solution of ditrazine citrate. The drug is administered subcutaneously into the neck area at a dosage of 0.016 g per 1 kg of animal weight. The next injection must be given after 24 hours. To destroy helminths and larvae, instead of ditrazine, you can use a 40% solution of loxuran at a dosage of 1.25 ml for every 10 kg of weight.
The drugs “Ivomec” and “Ivomec+” are also used for deworming. The solution is administered once, subcutaneously in the neck area, at a dosage of 0.2 mg per 1 kg of animal body weight. A good therapeutic effect is achieved by washing the affected eye with a solution of chlorophos (1%).
When treating thelaziosis in cattle, the following medications and solutions can also be used:
- febantel (rintal) orally (together with mixed feed) at a dosage of 7.5 mg per 1 kg of animal weight;
- Pharmacin (aversect-2) in a single dose of 1 ml per 50 kg of body weight;
- ophthalmic medicinal films (ODFs);
- a single injection of Fascoverm subcutaneously at a dosage of 5 mg per 1 kg of animal weight;
- tetramizole (20%) orally, a single dose of 7.5 g per 1 kg of weight;
- albendazole orally in a single dose of 0.0075 g per 1 kg of body weight;
- univerm orally twice every 24 hours at a dosage of 0.0002 g per 1 kg of weight;
- levamisole subcutaneously in a single dose of 0.0075 g per 1 kg of body weight.
For thelaziosis caused by the pathogen T. Rhodesi, it is effective to use solutions for washing the conjunctival area of the eye mucosa:
- iodine solution with a concentration of 0.05%;
- solution of 3% boric acid;
- emulsions of Lysol or ichthyol with a concentration of 3%.
You can treat the affected eye with an emulsion of ichthyol in fish oil. The composition is carefully injected using a syringe in an amount of 2 ml into the area of the third eyelid and gently massaged. The procedures are repeated three times every 2-3 days.
To treat the conjunctiva, you can also use infusions of medicinal herbs:
- tansy (fresh or dried);
- chamomile flowers;
- calendula;
- wild rosemary.
If complications occur in the second and third stages of the disease (purulent conjunctivitis, keratitis), the veterinarian prescribes antibacterial drugs.Most often these are sulfonamide drugs and substances of the penicillin group.
If there are ulcers on the cornea of the eye, you can use an ointment with novocaine and penicillin. When the cornea of the eye is clouded, freshly prepared ointment with potassium iodide is very effective.
For purulent conjunctivitis, it is recommended to treat with novocaine-chlortetracycline ointment, tanaceti liniment, or wash the affected areas with a furatsilin solution.
Prognosis and prevention
It is quite difficult to identify the disease at the initial stage. As a rule, the first obvious symptoms of helminth damage appear in the second and third phases of thelaziosis. Ignoring symptoms in the first stages leads to irreversible consequences. Without proper treatment, the animal may lose its vision. To prevent thelaziosis in cattle, it is necessary to carry out preventive deworming of livestock in the autumn and spring.
In order to identify symptoms of the disease in a timely manner, farm owners and private household plots must regularly conduct general clinical examinations of animals from May to September.
Cow flies are intermediate hosts of the parasite and are highly active during hot periods. On such days, it is recommended to keep the livestock under sheds or in pens, limiting grazing on pasture. It is also better to organize exercise for cattle at night. It is recommended to graze young animals separately from adult animals.
To combat carriers of thelasia larvae (cow flies), you can treat the skin and fur of animals with a solution of chlorophos (1%).
During the grazing period, it is recommended to feed phenothiazine-salt mixtures to young cattle - the drug causes mass death of larvae in the feces of animals.To exterminate flies on the surface of the animal’s body, the following drugs are used:
- ectomin concentration 0.1%;
- 0.25% solution of neostomazan;
- 1-2% dibrom emulsion;
- neocidol at a concentration of 0.1%.
Another option for preventing cattle from thelaziosis is the use of ear clips with pyrethroids. This option containing cypermethrin is a powerful means of combating insects and can reduce the incidence of thelaziosis in livestock by half.
Infection with bovine thelaziosis most often occurs on pastures in the summer. To treat premises, use ectomin (1-2%), neocidol emulsion with a concentration of 0.5% at the rate of 50-80 ml per 1 sq. m. After treating stalls and other premises, you cannot bring animals in immediately - you must wait at least two hours.
Conclusion
Thelaziosis in cattle is a rather dangerous disease that, without proper treatment, can lead to blindness. The manifestation of this pathology in cattle can be avoided by following a schedule of preventive measures. Most often, outbreaks of thelaziosis occur in the summer and autumn seasons. Therefore, during these periods it is necessary to carry out regular inspections of the cattle population on time.
How often does recovery occur or vision is restored, or the cow will be blind?