respiratory disease in animals vol 6 - سيريا فيت - الطب البيطري

د/عمرو · #1 10-04-2007, 12:50 صباحاً

Aspiration Pneumonia: Introduction
(Foreign-body pneumonia, Inhalation pneumonia, Gangrenous pneumonia
Aspiration pneumonia is a pulmonary infection characterized by inflammation and necrosis caused by inhalation of foreign material. The severity of the inflammatory response depends on the material aspirated, the type of bacteria aspirated, and the distribution of aspirated material in the lungs.

Clinical Findings:
A clinical history suggesting recent foreign-body aspiration is of greatest diagnostic value. Horses may develop fevers of 104-105°F (40-40.5°C), which can drop back into the normal range in a few days. Pyrexia is also seen in cats, dogs, and less commonly in cattle. The patient presents with acute dyspnea, tachypnea, and tachycardia. Associated findings are cyanosis and bronchospasm. A sweetish, fetid breath characteristic of gangrene may be detected, the intensity of which increases with disease progression. This is often associated with a purulent nasal discharge that sometimes is tinged reddish brown or green. Occasionally, evidence of aspirated material (eg, oil droplets) can be seen in the nasal discharge or expectorated material. On auscultation, wheezing sounds, pleuritic friction rubs, and crackling sounds of subcutaneous emphysema may be heard. In cows that aspirate ruminal contents, toxemia is usually fatal within 1-2 days. Cattle and pigs recover more frequently than horses, but mortality is high in all species. Recovered animals often develop pulmonary abscesses. In outbreaks after dipping of sheep, losses occur from day 2 to day 7 and then decrease gradually.
Lesions:
The pneumonia is usually in the anteroventral parts of the lung; it may be unilateral or bilateral and centers on airways. In early stages, the lungs are markedly congested with areas of interlobular edema. Bronchi are hyperemic and full of froth. The pneumonic areas tend to be cone-shaped with the base toward the pleura. Suppuration and necrosis follow, the foci becoming soft or liquefied, reddish brown, and foul smelling. There usually is an acute fibrinous pleuritis, often with pleural exudate.

Prevention and Treatment:
Atropine sulfate helps to control salivation stimulated by general anesthetics (eg, thiobarbiturates). Use of an endotracheal tube with an inflatable cuff prevents fluid aspiration during surgery.

The animal should be kept quiet. A productive cough should not be suppressed. Broad-spectrum antibiotics should be used in animals known to have inhaled a foreign substance, whether it be a liquid or an irritant vapor, without waiting for signs of pneumonia to appear. Care and supportive treatment are the same as for infectious pneumonias. In small animals, oxygen therapy may be beneficial. Despite all treatments, prognosis is poor, and efforts must be directed at prevention

Chlamydial Pneumonia: Introduction
Chlamydiae have been identified in various parts of the world as a cause of enzootic pneumonia in cats, calves, mice, sheep, piglets, foals, and goats. In cats, pneumonia may occur as a rare sequela of the more common chlamydial conjunctivitis and rhinitis. The main clinical sign of zoonotic chlamydiosis in humans is pneumonia, generally contracted from pet birds.

Etiology and Epidemiology:
The causative agent is Chlamydophila (Chlamydia)psittaci . Some respiratory isolates from calves have properties of immunotypes 1 and 6 and are similar to strains recovered from intestinal infections ([عزيزي الزائر يتوجب عليك التسجيل للمشاهدة الرابطللتسجيل اضغط هنا]) and abortions of cattle and sheep ( [عزيزي الزائر يتوجب عليك التسجيل للمشاهدة الرابطللتسجيل اضغط هنا]). Immunotype 6 has been recovered from pneumonic lungs of calves and pigs. Thus, the GI tract of carrier animals should be considered as an important site in the pathogenesis of chlamydial infections and as a potential source of the organisms. Infection most commonly occurs via inhalation of organisms from fecal carriers or other respiratory cases. Chlamydial pneumonia has affected calves under range conditions as well as on dairy farms. The disease in sheep is most frequently seen in feeder lambs assembled from different sources in feedlots or on irrigated pastures. Stressed lambs under these conditions are frequently subject to various secondary bacterial infections, which can result in higher mortality and morbidity rates than are seen in uncomplicated chlamydial respiratory infections.

Clinical Findings:
Calves, lambs, and goats with chlamydial pneumonia are usually febrile, lethargic, and dyspneic. They develop a serous and later mucopurulent nasal discharge with a dry hacking cough. Calves of weaning age are affected most frequently, but older cattle may also show signs.
Lesions:
The acute pulmonary lesion is bronchointerstitial pneumonia. The anteroventral parts of the lungs are affected but, in severe cases, entire lobes can be involved. The dry cough is attributed to tracheitis. Microscopic changes in the lungs include suppurative bronchitis and alveolitis progressing to type II pneumocyte hyperplasia and interstitial thickening due to an ingress of mixed inflammatory cells. Lymphocytic aggregates are frequently seen around airways and pulmonary vessels

Diagnosis:
Neither clinical signs nor lesions allow a definitive diagnosis of chlamydial pneumonia because they are not sufficiently different from those seen in the bovine or ovine respiratory disease complex. Diagnosis requires isolation of chlamydiae from affected tissues in tissue culture or chick embryo. Chlamydial inclusion bodies may be detected in affected tissues. Diagnosis may be supported by fluorescent antibody tests and serologic assays performed on acute and convalescent samples. Predominantly, IgG2 antibodies are induced by chlamydial infections in cattle. Subclinical chlamydial infections occur as well

Prevention and Treatment:
Vaccines are not available. Several antimicrobials (eg, penicillin, erythromycin, tylosin, and tetracyclines) can interfere with chlamydial replication, but tetracycline is generally the drug of choice. Treatment must start as early as possible and continue for at least 5-7 days

Hypostatic Pneumonia: Introduction
Hypostatic pneumonia is caused by passive or dependent congestion of the lungs, a condition most commonly seen in older or debilitated animals. Recumbent animals, such as those recovering from anesthesia, can develop hypostatic pneumonia if not repositioned regularly.

Blood is unable to pass readily through the vasculature of the lung, which can lead to a shift in fluid from the circulatory to the pulmonary spaces. It often occurs secondary to some other disease process causing chest pain (eg, congestive heart failure). Shallow respiration can lead to improper ventilation of the dependent lung, loss of surfactant activity, and accumulation of respiratory secretions and inflammatory exudate in lower airways. Compression of the abdominal contents in recumbent patients restricts the downward movement of the diaphragm, reducing tidal volume and ventilation of alveoli.

Coughing is not always a prominent clinical sign, but as the condition progresses, dyspnea and cyanosis become apparent. Secondary bacterial infection is common. Radiographs reveal increased pulmonary density, and the mediastinal space may show atelectasis.

The animal’s position must be changed hourly. Exercise should be encouraged insofar as it is compatible with the animal’s condition. If a primary cause can be determined, specific therapy should be instituted. Use of narcotics and sedatives should be minimal to encourage movement and to avoid suppression of the cough reflex. Proper hydration is important, but overhydration may increase congestion and should be avoided.

Mycotic Pneumonia: Introduction
Fungal infection of the lung results in an acute to chronic active, pyogranulomatous pneumonia.

Etiology:
Cryptococcusneoformans , Histoplasmacapsulatum , Coccidioidesimmitis , Blastomycesdermatiditis , Pneumocystiscarinii , Aspergillusspp , Candidaspp, and other less common fungi have been identified as causative agents of mycotic pneumonia in domestic animals (see also fungal infections, [عزيزي الزائر يتوجب عليك التسجيل للمشاهدة الرابطللتسجيل اضغط هنا]). Often these agents are found in immunocompromised hosts, but can cause disease in healthy individuals as well. Infection is typically caused by inhalation of spores, which can lead to hemolymphatic dissemination. Pulmonary tissues and secretions are an excellent environment for these organisms. The source of most fungal infections is believed to be soil-related rather than horizontal transmission. Considering the high rate of exposure to these pathogens in certain environments, there are unresolved questions on the epidemiology of the condition, including individual susceptibility, pathogenicity of organisms, the immune response of the host, and concurrent disease. Blastomyces and Histoplasma are prevalent in the Mississippi and Ohio River valleys, whereas Coccidioides is found in the southwestern USA and northwestern Mexico. Cryptococcus is often associated with accumulation of pigeon excreta

Clinical Findings :
Mycotic pneumonia is more commonly seen in small animals. Blastomyces infections typically occur in young, male, large-breed dogs. In cats, Cryptococcus has a predilection for the nasal cavity where it causes a granulomatous rhinitis and sinusitis. Acute, fulminant clinical presentations do occur but are rare, and the most common course of disease is chronic. A short, moist cough is characteristic. A thick, mucoid nasal discharge may be present. As the disease progresses, dyspnea, emaciation, and generalized weakness become increasingly evident. Respiration may become abdominal, resembling that of a diaphragmatic hernia

On auscultation, harsh respiratory sounds are heard. In advanced cases, breath sounds are decreased or almost inaudible. Tracheobronchial lymphadenopathy can cause extrinsic airway compression. Neutrophilic leukocytosis or neutropenia with a left shift, nonregenerative anemia, and periodic fever can occur, possibly concurrent with bacterial infections. Radiography will show enlargement of tracheobronchial lymph nodes and variable, nodular to linear, interstitial infiltrates.
Lesions:
Multifocal to coalescing lesions of granulomatous to pyogranulomatous inflammation are present in the lungs. Abscess formation and cavitation may be seen in conjunction with yellow or gray areas of necrosis. Causative organisms are present within macrophages or areas of intense inflammation. Dissemination to multiple organ systems (eg, skin, eyes, peripheral lymph nodes, bones, CNS, male genitalia, oral cavity, nasal cavity) may occur.

Treatment:
There is no entirely satisfactory method of treating systemic mycotic infections. Amphotericin may be helpful but is undesirably nephrotoxic. Ketoconazole, and several newer antifungal agents such as itraconazole and fluconazole, show better, but variable, results against fungal pathogens in companion animals. Protracted therapy, at least 2 mo beyond clinical resolution, is usually necessary for resoluton of the infection

عبد الله الطيباني · #2 25-04-2007, 07:12 صباحاً

عمل ومجهود ممتاز . شكراً يا زميل بارك الله فيك

dr_waleed04 · #3 23-08-2007, 11:32 مساء

يعطيك العافية و تسلم

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