Harmfulness of sheep rhinomiasis and its control

Sheep rhinomiasis is a parasitic disease caused by Drosophila nasi parasitic in the nasal cavity and cranial sinus of sheep. In recent years, in the sheep flocks fed by farmers in our area, due to the lack of attention to the prevention and control of rhinosomiasis, the infection rate of rhinomiasis increased rapidly, which affected the normal growth and development of sheep and seriously affected the fattening effect of sheep. Through the systematic investigation and observation of prevention and treatment of sheep rhinosiasis in farmers and farms, the author has achieved good results. the report is as follows:

I. pathogen and its life history

1. Adults: about 25mm in size, with a large head, protruding forehead, and many bag-shaped depressions in the lateral frontal region, with one hair from each depression. Beak degeneration, do not bite animals, can not eat. The antennae are short, the base of the antennae is very strong, the distal end is slender and weak, the distance between the two antennae is less than the diameter of the third section of the antennae, and the antennae awn is hairless. The feet are short, the wings are small and transparent, the fourth longitudinal vein meets the third longitudinal vein, the first posterior chamber is closed, the transverse suture of the middle chest dorsal plate is complete, the chest hair is missing, but there is long hair. The glands are quite large, the abdomen is wide, and the abdomen is short. The surface of the body is gray, but there are irregular and shiny gray spots.

Sheep nose fly adults generally begin to appear from February to April, especially in summer, are generally out of business in winter, and their life span is generally 3-6 days, no more than 20 days at most. After Eclosion, the adults can mate within 1-3 days, and often crawl in the corner or some dark places at night and early in the morning. After dawn, especially when the weather is hot at noon, they often fly around the sheep and produce larvae around their nostrils. The sheep are so afraid of the flies that as soon as they hear the sound of flying or see it fly, they run wild, often pressing their nose to the ground or pressing their nose against other sheep to avoid its attack.

2. Larvae: the initial larvae are about 1mm long and 25mm 32mm long after growth. the larvae are stout, the back is arched, the abdomen is flat, the front is not too thin, the third instar larvae have a pair of strong and curved black mouth hooks, and there are numerous small thorns on the ventral side of each segment. not on the back. The front valve is not prominent or missing, and the back end consists of a pair of D-shaped valves made up of small plates with many small holes.

Sheep nose fly larvae produced by adults around the sheep nostrils, gradually crawl into the nostrils, all the way to the frontal cavity of the skull, but also very few climb into the trachea, bronchi, eyes, ears and other tissues and organs. It is attached to the mucosa, develops gradually, and develops to the third stage larvae in the nasal cavity and frontal sinus. After maturing, the third stage larvae gradually move to the nostrils, spray out of the ground when the sheep sneeze and drill into the soil. According to the difference of climate, it changed from pupa to adult nose fly after about 1 ~ 2 months. The adult sheep nose fly generally lasts for 1 or 2 generations a year in our district.

Second, the harmfulness of sheep nose flies

1, general harmfulness: sheep in the nose fly activity season, because of fear that the nose fly maggot makes the sheep nervous, avoid everywhere, can not rest assured in the sun grazing and grazing, affecting sheep fattening.

When the larvae enter the nasal cavity of the sheep, the mouth hook of the larva is pierced into the nasal passage. the mouth hook and small thorns stimulate the mucosa of the nasal cavity and frontal sinus, causing inflammation of the mucosa of the nasal cavity. The affected sheep often have nasal mucus, which changes from dilute to sticky, and finally becomes purulent, and it is difficult to breathe. At the same time, because the larvae have thorns on the ventral side and hooks on the head, when crawling in the nasal cavity, the sheep are often stimulated to sneeze, which makes the sheep eat and sleep uneasy. in addition, the nasal suppurative products are absorbed by the sheep, and even cause systemic weakness and malnutrition, and finally make the sheep gradually lose weight: some will cause death.

Sheep rhinomiasis is often diagnosed according to clinical symptoms, epidemiology and sheep autopsy data (larvae are found in the nasal cavity and frontal sinus). In the past 20 years, the author examined 467 sheep slaughtered, died of disease and other causes, and the cumulative detection rate was 87.6%. The detection rate of sheep was almost 100%, especially from the end of summer to the end of winter. 64 larvae were found in the nasal cavity of a sheep.

2. Special harmfulness: very few larvae crawl into the trachea, bronchi, eyes, ears, brain and other organs of sheep to cause corresponding symptoms. In April 1989, September 2000 and October 2001, a sheep was found to have a sudden cough, frequent painful coughing, and soon elevated body temperature, and finally asphyxiated to death. After autopsy, it was found that there were nasal flies in the trachea, which caused lobar pneumonia in sheep. A sheep was found to be blind in October 2000 and May 2002 respectively, and nose flies were found behind the eyeball of the sheep after Tu Han's autopsy.

III. Prevention and treatment of sheep rhinosomiasis

1. It is difficult to eliminate sheep nose flies, and we must strictly implement the policy of "prevention is more important than control". In January, February and March of early spring, farmers can be mobilized to dig maggot pupae in the corners around the sheep pen to destroy them. Usually, if you find sheep nose flies adults in the corners and shadows every morning, they should be inactivated at any time.

2. In the epidemic season of sheep rhinomiasis, 3% Laisuer solution was sprayed into the nasal cavity of sheep, and the effect of killing sheep nose fly larvae was very good. In late spring, early summer and early autumn, and at the end of autumn and early winter, 836 sheep rhinus fly larvae fed by farmers and farms were sprayed through nasal cavity to kill sheep nose fly larvae. The method is Keep the sheep lying on the side at a downhill of about 20-30 °, head down and tail up (to prevent spraying liquid into the trachea and lungs of the sheep to avoid causing foreign body pneumonia and tissue necrosis), use a sprayer with a diameter of about 5 mm, a length of about 15 cm: the front end is closed and a small rubber tube with small needle holes is inserted into the sheep's nasal cavity (the insertion depth depends on the size of the sheep. It is best to try it outside, with the length from the end of the sheep's nose to the fovea of the eye 2-3 cm), spray 15-20 ml 3% Lysol solution into each nostril. Spray liquid after the increase in a single nose, like to sneeze, often will kill the nasal fly larvae ejected. After 5 days of deworming, the deworming effect was checked, and the deworming rate was about 90%.

According to the active season of sheep nose flies, the effect of repellent can only be achieved once. After the adult activities of nose flies, sheep can still be infected as usual. In practical work, nasal spray can be carried out for many times according to the activity of sheep nose flies. According to the author's clinical experience, it is appropriate to dispel nasal flies three times in the peak season, autumn and later stage of nasal fly activity.

In addition, you can also sprinkle some lime in the sheepfold to make the sheep's nose touch the ground, encourage the sheep to sneeze, and exterminate the nose fly larvae. This method can be used by farmers at any time according to the infection of sheep nose flies to sheep, but the deworming effect of this method is not high, and generally only part of the larvae can be spurted out by sheep.

The prevention and control of sheep nose flies is still under exploration, and it is still impossible to control and avoid repeated infection in sheep, and some sheep will be infected with the disease soon after spraying liquid. The control of sheep nose flies needs to be further studied.