DISEASES OF RESPIRATORY SYSTEM

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Disease of nasal cavities and sinuses

Nasal myiasis

Nasal bot, head bot, head grub

Definition:

It is a chronic rhinitis and sinusitis of sheep characterized by persistent annoyance and mucopurulent discharge and is caused by invading maggots. This disease presents in all sheep-producing countries and maintains high incidence in flocks.

Occurrence:

• This disease occurs in all breeds, sexes and ages of deep.

• In warm countries both adult and larval phases of the disease persist throughout all seasons, but in temperate zones, adult flies emerge, mate and oviposit only during summer and myiasis continues throughout the cold seasons.

Etiology

• Oestrus ovis is the prevalent fly cause nasal myiasis.

• Both the adult insects and their larvae attack sheep.

Pathogenesis

1. Mated female deposit 500 larvae on the nostrils of sheep.

2. The first larval stages enter the nasal cavity and feed on the mucus and desquamated cells. Then first larval stages molt into second larval stages.

3. The second larval stages pass into the frontal and maxillary sinuses where they grow into third stage larvae mature larvae.

4. After 2-10 months, the mature larvae return to the nostrils and are sneezed to the exterior. They enter the soil and pupate through a period of 27 to 36 days.

Pathogenesis (cont’)

1. Adult females deposit larvae throughout the summer in temperate zones and throughout most seasons in hot zones

2. the movement of numerous maggots in the nasal cavities, paranasal sinuses annoy the hosts, and animal’s feeding.

3. In the sinuses, the larvae produce allergic and inflammatory reactions. These changes cause discomfort and interrupt the animal’s feeding.

4. Some larvae wander along the trachea into the lungs producing fatal reactions.

Oestrus ovis life cycle

Larvae within nasal sinus

Clinical signs :

1. Sheep attacked by ovipositing flies stamp with their feet, shake their heads, sneeze, and blow and ram their noses against the ground or other sheep.

2. In some cases, these acts traumatize and infect the nostrils.

3. The animals also seek cool areas such damp shade where the flies do not frequent.

Clinical signs (cont’)

4. During the time the larvae occupy the nose and sinuses, affected sheep may hold their heads towards the ground and persistently discharge mucopurulent exudate from the nostrils.

5. Breathing may be difficult due to swollen nasal membranes and plugged nostrils.

6. The morbidity may reach 80% of a flock, but mortality is nil. The course of adult fly attack periodically extends through the summer and the rhinitis and sinusitis continue up to 10 months.

Oestrus ovis in nostrils of sheep

Mucopurelent nasal discharge in sheep bot

Diagnosis :

• Restlessness behavior of sheep during hot-mid –days and observation of the fly.

• Chronic nasal discharge and finding of larvae in sinuses confirm myiasis.

Treatment

• Sheep should be treated for nasal myiasis during autumn as larvae are small. Killing of mature larvae in the sinuses may result in severe reaction in the sinus membranes.

• Either of the following compounds and dosage rates are highly effective.

• Rafoxinide administered orally at dose rate of 7.5 mg/kg, B.wt • Ivermectin at the rate of 50 ug/kg B.wt Ivomic, Iveen,

Ivomax, uvemic, avimic.

•Important

Pharyngitis

• DefinitionInflammation of pharyngeal mucosa characterized

clinically by coughing and painful difficult swallowing

Etiology1. Pharyngeal trauma usually results from aggressive use of

equipment used to administer oral medication (e.g., balling guns, dose syringes, oral speculums, and stomach tubes).

2. Injuries may result in the formation of discrete abscesses or extensive and diffuse cellulitis, both of which can interfere with swallowing and possibly lead to respiratory difficulty or distress.

3. Bacteria commonly isolated after an incident of pharyngeal trauma include Actinomyces, Pasteurella multocida, Pasteurella haemolytica, and Fusobacterium.

4. Corynebacterium pseudotuberculosis, the causative agent of caseous lymphadenitis in sheep and goats may localize in the regional lymph nodes of the head, especially the pharyngeal lymph nodes.

Clinical Signs

• Sheep with pharyngitis have a normal desire to eat and drink but may have difficulty swallowing.

• Coughing.• Respiratory distress in pharyngeal abscess.

Diagnosis

• Case history• Clinical signs• Endoscopic examination

Treatment

• Antimicrobial: antibiotics (oxytetracyclines, gentamycin, streptomycin) or sulphonamides.

• Anti-inflammatory: corticosteroids such as dexamthazone or NSAID such as diclofenac.

• Surgical drainage of abscesses.

Laryngitis

• Definition: an inflammation of the mucosa or cartilages of the

larynx, leading to coughing

Etiology:

• May result from upper respiratory tract infection• Direct irritation from inhalation of dust, smoke, or

irritating gas; foreign bodies; or the trauma of intubation, excess vocalization,

• Injury from roping or restraint devices. • Bacteria: Laryngitis may accompany

Fusobacterium necrophorum or Corynebacterium pyogenes infections in sheep.

Clinical Signs• A cough is the principal sign of laryngitis when edema is

slight and the deeper tissues of the larynx are not involved. It is harsh, dry, and short at first, but becomes soft and moist later and may be very painful. It can be induced by pressure on the larynx, exposure to cold or dusty air, swallowing coarse food or cold water.

• Stridor may result from swelling and reduced motion of the arytenoid cartilages.

• Halitosis (bad breath) and difficult, noisy breathing may be evident, and the animal may stand with its head lowered and mouth open.

• Fever in infectious causes.

Diagnosis

• Case history• Clinical signs• Endoscopic examination (laryngoscope).

Treatment

1. Corticosteroids should be administered to reduce the obstructive effect of the inflammatory swellings.

2. Concurrent administration of NSAID (Declofenac 1 mg/kg BW IV) and systemic antibiotics is also necessary.

3. Administration of diuretic drugs, eg, furosemide, may be indicated for resolution of laryngeal edema if present.

Questions