Bacterial and viral diseases

Tuberculosis

►It is a chronic diseases ( may acute or sub acute ) of man andanimals caused by mycobacterium tuberculosis.There are 3 common types of tubercle bacillus:1- Human type M. tuberculosisThis affects man, cattle and pigs ( lesser extent ) it is only ofimportance in animals as it causes reaction to the tuberculin testin cattle.2- Bovine type M. BovisThis affects man, cattle and pigs. It is most virulent for cattle and pigs.3- Avian type M. aviumThis affects birds, pigs and to a much lesser extent cattle and sheep.

Tuberculosis

►It is interesting to note that sheep are rarely infected with T.B.

There is a fourth type which affects fishmode of infection:1- Respiration 2- Ingestion3- Inoculation 4- Genital 5- Congenital

Lymph nodes

T.B. can remain viable over 2 year in frozen carcass (-9C). 18 day in pickled meat. 167 days in decomposed lungs as decomposition has no

effect

Pathogenesis

●Infection of animals especially T.B. digestive system (pig) or respiratory (cattle) exudation of fluid + involvement of Reg. l.n . Or ●if bacilli are few in number.

●less in virulence. ●if the defensive powers of the body are high T.B.undergo necrosis, cassation and calcification primaryinfection ( Chronic form chronic generalization ) raises thebody resistance against a second infection. ( Allergic resistance )

Pathogenesis

►When the defensive power of the body is low Reification exogenous and endogenous ● Acute haematogenous military T.B.

Chronic localized organ T.B. Chronic isolated organ T.B.►Chronic isolated organ T.B.a- chronic acino nodular T.B of the lungs.b- lung cavitation.c- chronic T.B of the udder.d- chronic T.B of the testes.

Pathogenesis

►Spreading of T.B by pre –existing channels.( Bronchi- milk ducts- semen porous tubule) ● lymph or blood stream is not invaded.●L.n is not infected but if infected primary infection.

Reinfection acute late generalization Stress factor body resistance virulence, profuse

exudation dilute bacteria spreading via pre – existing channels, lymphatic or haema-togenous channels

Break down of T.B

1- multiple lobular caseous pneumonia.2- acute acinonodular of the lungs.3- caseous pleurisy.4- caseous nephritis.5- caseous metritis.

6- caseous mastitis.

Break down of T.B

Macroscopically appeared as dry cascous masses interspersed with blood spots + regional L.n. continuous supply of T.B. blood.

►T.B. in pigs. (Bovine Type) Primary infection digestive system of tonsils sub

maxillary L.ns ●lesion may be healed.Or break down Lymph heamatog enous generalization

Miliary T.B.

Break down of T.B

►Avian T.B. in pigs:● tissue reaction is of production type .Tumour like lesion (no cassations or calcification)● L.ns are enlarged, firmer, no tubercle.In later stage small discrete yellow foci or large areas ofnecrosis at the centre of L.n (early enucleated from L.n ).

T.B. of different organs and tissues

1-T.B. of lungs:a- Isolated encapsulated and calcified foci:When the primary lesion present a limited area of bronchi

pneumonia +regional L.n healing fibrosis + calcify.b- Chronic acino-nodular and cavitation:When scattered case us foci of various sizes involving the

acini of one or both lungs and emoceses by fibrous C.T separate it from surrounding healthy tissues chronic acinened .

T.B. of different organs and tissues lung cavitations: are example of chronic organs T.B. and

caused by reinfection via spreading though the bronchi the blood or lymph and L.n are free. If the lesion present in L.n old and calcified primary inf.

L.c. appear as solid cereous area liquefied enter the main bronchus cavity in the upper caudal parts of the main lung lobes the cavity has a congested wall and contain yellow-ish purulent material.

T.B. of different organs and tissues T.B. areas in lungs are surrounded by healthy pulmonary

tissue or zone of hepatization. c-Acute acino-nodular :As caseous foci of even distribution of one or both lungs

break down of body resistance spreading ● localized ● haem►haematog enous spread:L.n is show signs of recent infection Military T.B. are seen the lungs, liver and kidney cortex.

T.B. of different organs and tissues

►localized spread:a- L.n is either free or show old calcified lesion primary

infection.b- no military T.B. in the lungs or else where.c- caseous pneumonia:this mean coalescence of caseous lung tissue,

interspersed with blood spots these areas sharply separated from the healthy tissues by a zone of inflammation encapsul.

T.B. of different organs and tissues► Late generalization:Its importance revealed to it lead to acute military T.B. of

both wng regional L.n is unaffected.The bacilli present in the blood and meat in 80-90% of

cases.e- early generalization:Miliary T.B. uniformly disturb

same age and size.● The lungs are enlarged, heavy edematous and

emphysematous ehanges.● L.n. is quite enlarged show caseation of a stellate

appearance.● Bacilli muscle of blood in 70%

T.B. of different organs and tissues

► Tuberculosis tracheitis and laryngitis: Appearas nodules or ● ulcer on mucous membrane.● due to coughing of T.B. materials.►T.B. of pig lungs due to avian bacilli:●is of productive nature.●especially caseation or calcification.●lesion appear as metastatic tumours.●L.ns are enlarged and appear unaffected pleura

T.B. of different organs and tissues

In cattle visceral T.B pleurisy is more common than the parietal T.B pleurisy.

Methods of infection:a- lung infection direct lymphatic drainage visceral

pleura pleural cavity.b- Rarely by direct haematogenous spread:c- Rarely from the peritoneum by lymphatics of the

diaphragm.d- Rupture of lung lesion or thoracic L.ns.

T.B. of different organs and tissues

The acute from:●It is mainly during late generalization.●the pleura is thickened to 1 inch or more and composedof a dry caseaus material interspersed especially bloodspots.●massive entry of bacilli blood stream acute case

us pneumonia.

T.B. of different organs and tissues

The chronic form:● in early stages nodules soft, reddish velvety

granulation enter in ehronic generaliz coalese forming large casrous.

Masses, varying in size typical grapes form. ●the pleura is very much thickened.●on section, there is dry caseous moss especially

calcified center.

T.B. of different organs and tissues

►In pig:T.B. of serous membranes are not common in pigs.●The lesions appear as :Small, scattered nodules grains on palpation may

penetrate to the sub- pleural tiss.●The lesions may be of the diffuse type.PeritoneumT.B. peritonitis occur either in caver or in adults .

T.B. of different organs and tissues

►In calves:The infection extension from a primary lesion from the

liver.The lesions are found in the peritoneum and diaphragm

which in contact especially anterior surface of the live

T.B. of different organs and tissues►In adults:a-direct extension of infection from liver or uterus.b-from pleura peritoneum ( by lymphatle of the

diaphragm)c-breakdown lesions of lungs ingestion of massive

doses of bacini into the digestive tract infection of the mesenteric L.ns

T.B. of different organs and tissues

T.B. of pleura and peritoneum may occur especially entery of bacilli into the systemic civeulation chronic T.B. of pleura of peritoneum is not serious in judgment.

The pericardiumT.B. pericarditis extension of infection from T.B.pleurisy.T.B. appear as red velvety patches near the base of theheart or as a caseous nodules involving the wholepericardium.T.B. lesions of the myocardium or the endocardiumare rare.