4

Pneumonia

Pneumonia is the inflammation of the pulmonary parenchyma usually accompanied by inflammation of the bronchioles and often by pleurisy. It is manifested clinically by an increase in respiratory rate, cough, abnormal breath sound on auscultation and in most bacterial pneumonia, by evidence of toxemia.

Causes:

a-Cattle:
Pneumonic pasteurellosis (Shipping fever). Pasteurella hemolytica, P.multocida with or without parainfluenza 3 virus (PI3).
Enzootic pneumonia of calve: PI3, adenoviruse 1,2, and 3 Rhinovirus, Bovine Syncytial Virsus (BSV), reoviruses, Bovine herpes virus l (BSV virus) plus chlamydia spp. Mycoplasma spp. Pasteurella spp. Corynebacterium pyogenes, Strept spp. and bedsomia spp. (Actinobacillus actinoides).
Viral Pneumonia of yearling and adult cattle is caused by either PI3 or adenoviruses.
Contagious bovine pleuropneumonia caused by Mycoplasma mycoides.
Atypical interstitial pneumonia.
Massive infestation with ascarid larvae.
Lungworm pneumonia (Dictycolus viviparous).
Klebsiella pneumonia infection in calves and nursing cows suffering from mastitis caused by this organism.
Sporadically in T.B. (Mycobacterium bovis).
Sporadically in calf Diphtheria (Spherous necropherous).
Hemophilus somnus, possibly in young cattle affected with the more common septicemic form of the disease. Its role as primary cause is uncertain.

Horses:

Newborn foals: Any of the septicemia which occur at those time, Strep. Sp., E. Coli, Actinobacillus equi.
In immunodeficient foals, pneumonia is caused by adenoviruses or pneumocystis carini.
Older foals: Corynebacterium, Rhodococcus equi and equine herpesvirus.
Dictycaulus arnifeldi and Parascarsis equorum rarely cause significant pneumonia.
As a sequel to Strangles.
Rarely as sequele to equine viral arteritis or equine viral rhinopnumonitis in adultanimals.
Glanders and epizootic lymphangitis (Histomonus farcinicus) usually include pneumonic lesions.


Sheep:
Pneumonic pasteurellosis (Pasteurella sp.) as acute primary pneumonia in feedlot lambs, or secondary to PI3 or Chlamedia spp.
Newborn lambs: Uncommonly Strept. Zooepidemicus, Salmonella abortus ovis.
Mycoplasma spp. (Severe pneumonia).
Symptomless pneumonia without secondary infection adenovirus, RSV, reovirus Mycoplasma sp.
Corynebacterium pseudotuberculosis (sporadic).
Melioidosis (Pseudomonus pseudomallei).
Lungworm pneumonia (Dictycolus filaria).
Progressive interstitial pneumonia.

Goats:

Pleuropneumonia caused by Mycoplasma strain F38 or M.Capri is a devastating disease.
Chronic interstitial pneumonia with pulmonale as common sequel by a number of Mycoplasma spp. M . mycoides var. mycoids appears to be the most commonly recorded.
Rotavirus infection.

All species:

Toxoplasmosis (sporadic cases).
Systemic mycosis lesion are focal only.
Aspiration pneumonia.
Secondary pneumonia caused by Strept. Spp. Corynbact.spp. dermatophilus sp.


Pathogenesis:
Under normal condition the major airway and the lung parenchyma prevent the entry of and neutralize or remove injurious agents, so that the lung contains very few, if any organism beyond the terminal lung agents.
Many infections of the respiratory tract originate from aerosolized particles carrying infectious agents, which arise external to or within the respiratory tract. Thus the pathogenesis of respiratory infections is related to the depletion of particles and infectious. Lung clearance mechanism:-
The major defense mechanisms of the respiratory tract include aerodynamic filtration by the nasal cavities, sneezing, local nasal antibody, the laryngeal mechanism, the alveolar macrophages and the systemic and local antibody systems.
Anything which interferes with the clearance of particles from the upper mucous will interfere with the clearance of particles from the upper respiratory tract. The cough reflex provide an important mechanism by which excess secretions and inflammatory exudates from the lungs and major airway can be removed from the airway and disposed of by expectoration or swallowing.
In animal with relatively normal lugs, coughing represents a very effective means of expelling materials. In the presence of severe trachitis and pneumonia, coughing may results in retrograde movements of infected material to the terminal respiratory bronchioles and actually promotes spread of the infection to distal parts of the lungs.
The lung clearance mechanism may be affected by a concurrent viral infection. This may have major implication in the control of some of the common infectious respiratory disease of farm animals.
In high altitude and during periods of active physical or metabolic activity, the occurring low oxygen tension or hypoxia may follow mucociliary and macrophage activity and decrease pulmonary clearance rates. The basal ventilation activity is comparatively greater than other mammals, which results in that the inspired air becomes progressively more contaminated with infectious, allergic, or noxious substances.
The bovine lung also has a higher degree of compartmentalization than other species. This may predispose to airway hypoxia peripheral to airway, which become occluded. This results in reduced phagocytic activity and retention or multiplication of infectious agents. In addition, because of the low number of alveolar macrophages in the bovine lung the pulmonary clearance mechanism may not be effectively as in other species. There is also a low level or atypical bioactivity of lysozyme in bovine respiratory mucous which may make cattle more susceptible to infection of the respiratory tract than other species.

Clinical findings:

Rapid, shallow respiration is the cardinal signs of early pneumonia, dyspnea occurring in the later stages.
Polypnoea may be quite maker with only minor pneumonic lesions and the rapidity of the respiration is an inaccurate guide to the degree of pulmonary involvement.
Cough is other important sign (the type of the cough varies with the type of the lesion). Bronchopneumonia is usually accompanied by a moist painful cough, interstitial pneumonia by frequent, dry, backing cough, often in paroxysms.
Cyanosis is not a common signs and occurs only when large of the lung are affected.
A nasal discharge may or may not be present in the bronchioles whether or not there is accompanying inflammation of the upper respiratory tract.
The odour of the breath may be informative. It may have an odour of the decay when there is a large accumulation of inspissated pus present in the air passages, or putrid, especially in horses, when pulmonary gangrene is present.
Auscultation of the thorax before and after coughing may detect exudate in the air passages.
By auscultation in the early congestive stage of bronchopneumonia and interstitial pneumonia the vascular murmur is increased. Moist rales develop in broncho- pneumonia as bronchiolar exudation increases but in uncomplicated interstitial pneumonia, clear, harsh bronchial tones are audible. When complete consolidation occurs in either forms, bronchial tones are the only sounds audible over the affected lung but moist or cripitant rales can be heard at the periphery of the affected area in bronchopneumonia.
Consolidation also causes increased audibility of the heart sounds. When pleurisy is also present it causes a pleuritic friction rub in the early stages and muffling of the pulmonary sounds in the late exudative stages. Consolidation can be detected also by precussion of the thorax or by tracheal percussion.
There may be an observable difference in the amount of movement in the two side of the chest if the degree of consolidation is much greater in one lung. Additional signs evident in pneumonia include fever of variable severity, anorexia, depression, and an increase in pulse rate.


In chronic bronchopneumonia in cattle:
There is toxemia with rough hair coat. Respiratory and heart rates are above normal and there is usually a moderate fever.
The depth of respiration is increased and both inspiration and expiration are prolonged. A grunt expiration and open mouth breathing indicate advanced pulmonary disease.
A copious bilateral mucopurrulent nasal discharge and a chronic moist productive are common.
On auscultation of the lungs loud bronchial tones are usually audible over the ventral half of the lungs and moist dry rales are commonly audible over the entire lung fields, but are most pronounced over the ventral half.
With adequate treatment in the early stages, bacterial pneumonia usually responds quickly and completely but viral pneumonia may not respond as it may relapse after an initial response.
Thetreatment responses is probably due to control of secondary bacterial invaders. In some bacterial pneumonia the same course is apparent due to either reinfection or persistence of the infection in necrotic foci out of the reach of usual therapeutic measures.

Clinical pathology:

Anti-mortem laps. Examination consists largely of cultural examination of nasal swab or tracheal sputum and determination of the sensitivity of the isolated bacteria to antibacterial agents.
Transtracheal aspirations have been described earlier and is valuable tool for an intensive investigation of a respiratory tract infection.
Radiographic examinations are undertaken only in animals of suitable size.
Hematological examination usually reveals a leukocytosis with shift to the lift in bacterial pneumonia.
A leukopenia and lymphopenia occurs in some cases of acute viral pneumonia. In viral pneumonia, the serological testing of acute and convalescent sera, in addition to the isolation of the virus, are useful tools supports in evidence of the presence of an active infection.

Diagnosis:

There are two kinds of errors in the clinical diagnosis of pneumonia.
One of that the pneumonia is not detected clinically, because the abnormal lung sound are apparently not obvious.
The other is to make a diagnosis of pneumonia, because of the presence of dyspnoea which was due to disease in some other body systems.
The major clinical findings of pneumonia are polypnoea in the early stage and dyspnoea later, abnormal lung sounds, and fever and toxemia in bacterial pneumonia. Polypnoea and dyspnoea may result from involvement of other body systems as congestive heart failure, terminal stage of anemia, poisoning by histotoxic agents such as hydrocyanic acid, hyperthermia and acidosis are accompanied by respiratory embarrassment, but not by the abnormal sounds typical of pulmonary involvement. Pulmonary edema and congestion, embolism of the pulmonary artery and emphysema are often mistaken for pneumonia, but can be usually differentiated by the absence of fever and toxemia, on the basis of the history and on auscultation findings.
All of the practical lab. Aids described should be used when necessary. They are of particular importance when outbreaks of pneumonia are encountered. In a single routine cases of pneumonia the cause is usually not determined.
However the age and class of the animal, the history and epidemiological findings and the clinical findings can usually be correlated and a presumptive etiological diagnosis done.


Differential diagnosis:
Differential diagnosis must be done from pleurisy, that characterized by shallow, abdominal type of respiration, pleuritic friction sounds when effusion is minimal and a muffling of lung sound and a fluid line detectable by auscultation and percussion when fluid is plentiful.
Differential diagnosis must be done from pneumothorax, where the later have inspiratory dyspnea and on the affected side the abnormalities include; an absence of the vesicular sounds, but bronchial tones are still audible over the base of the lungs, an increase in absolute intensity of the heart sound and increased resonance on percussion. Finally differential diagnosis must be done from diseases of the upper respiratory tract such as laryngitis, and tracheitis which are accompanied by varying degrees of inspiratory dyspnea which is often loud enough to be audible without stethoscope.
In less severe cases, auscultation of the mid- cervical trachea will reveal moist wheezing sounds on inspiration. These sounds are transmitted down into the lungs and are audible on thorax auscultation.
In some cases of severe laryngitis and tracheitis, the respiratory sound are audible over the trachea and over the lungs are markedly reduced because of almost total obliteration of these organs.
In laryngitis and tarcheitis there is usually a more frequent cough than in pneumonia an the cough can be readily stimulated by squeezing of the larynx or trachea.
In pnumonia the abnormal lung sounds are audible on both inspiration and expiration. Examination of the larynx through oral cavity in cattle and with the aid of rhinolaryngeoscope in the horse will usually reveal the lesions.

Treatment:

In specific infection isolation of affected animals and careful surveillance of the remainder of the group to detect cases on the early stages should accompany the administration of the specific antibacterial drugs or biological preparations to affected animals. The choice of antibacterial agents will depend on the tentative diagnosis, the experience with drugs in previous cases and the results of the drug sensitivity tests.
The common bacterial pneumonia of all species will usually recover quickly (24 hr.) if treated with an adequate dose of the drug of choice early in the course of the disease.
Animals with severe pneumonia will require daily treatment for the several days until recovery occurs.
Those with bacterial pneumonia and toxemia must be treated early on an individual basis. Each case should be identified and carefully monitored for failure to recover.
Antimicrobial agents in a long acting base may be used to provide therapy over a 4-6 day period instead of the daily administration of the shorter-acting preparations. However, the blood level from the long-acting preparations are not as high as the shorter-acting preparations and may not be as effective in severely affected animals.
The common causes for failure to respond favourly to treatment for bacterial pneumonia include:
A) Advanced disease when treatment was undertaken.
B) The development of pleurisy and pulmonary abscesses.
C) Drug resistant bacteria.
There is no specific treatment for the viral pneumonia because viral and mycoplasmal pneumonia are commonly complicated by secondary bacterial infections. It is common practice to treat acute viral and mycoplasmal pneumonia with antibacterial until recovery is apparent.
In outbreaks of pneumonia where many animals are affected and new cases occur each day for several days, the use of mass medication of the feed and / or water supplies should be considered.
Mass medication may assist in the early treatment of subclinical pneumonia and is a labor-saving method of providing convalescent therapy to animals which have been treated individual.
When outbreaks of pneumonia occur and new cases are being recognized at the rate of 5-10 % pre day of the total in the group, all the remaining in contact animals may help to treat subclinical cases before they become clinical and thus abort the outbreak.
Corticosteroids have been used for their anti-inflammatory. Effect in the treatment of acute pneumonia. However, there is no clinical evidence that they are beneficial. Affected animals should be housed in warm, well-ventilated, draft-free accommodation, provided with ample, fresh water, and light nourishing food.
During convalescence condition, the return to work or exposure to bad or cold weather should be avoided. If the animal does not eat, oral or parentral force-feeding should be initiated. If fluids are given intravenously care should be exercised in the speed with which they are administered. Injection at too rapid rate may cause overload on the heart ventricle and death may occur due to acute heart failure.
Supportive treatment may include the provision of O2 supply to be available especially in the critical stages when hypoxia is evident. In foals, the oxygen can be administered through an intranasal tube passed back to the nasopharynx and delivered at the rate of about 3 liters / min. for several hours. Expectorants may be of value in chronic cases and during convalescence.