Brucellosis

Brucellosis (undulant fever) affects primarily the reticuloendothelial system, the joints and at times the reproductive organs, heart, vessels, lungs, meninges and kidneys. Three organisms, B. melitensis, B. abortus, and B. suis may produce the disease. The reservoir of infection is in goats, cattle and pigs. Infection occurs through contaminated milk or through meat handling. The organ­isms lodge in the lymph nodes and then in the blood stream. Diagnosis is confirmed by agglutination of Brucella organisms by the patient's serum. In the common nonfatal form there is a low-grade undulating fever. loss of weight, cough or gastro-intestinal symptoms with enlargement of the lymph nodes and spleen. These symptoms may persist intermittently for years. A maculo-papular skin eruption and arthritis may occur. The characteristic lesion is granulomatous with an infiltrate of epithelioid cells, macrophages and giant cells resem­bling the Reed-Sternberg cell of Hodgkin's disease. In rare fatal cases with septicemia there is necrosis of lymphoid tissues and widespread thrombophlebitis. Infected em­boli may produce mycotic aneurysms.

Infectious Splenomegaly

Hyperplasia of the spleen with infectious disease may be acute or chronic. Acute hyperplastic splenitis (acute splenic tumor) occurs with septicemia or in the presence of severe pyogenic infections. The spleen is enlarged and soft. The follicles may be enlarged and phagocytosis is active.
In protozoan and bacterial diseases that affect the reticuloendothelial system, such as visceral leishmaniasis, African trypanosomiasis, malaria, etc., the enlarged spleen acts as a clearing house for phagocytosis and is engorged with parasites and para­sitized macrophages.With chronic splenic hyperplasia found in advanced stages of syphilis, tuberculosis, brucellosis, malaria, leishmaniasis, trypanosomiasis, schistosomiasis and infectious ar­thritis (Felty's syndrome) there is increase of both the lymphoid and connective tissue elements. The capsule is often thick and opaque. There may be endothelial hyper­plasia and hyalin changes in the arterioles. The infectious diseases of the spleen and reticuloendothelial system are:

(1)Infectious mono nucleosis
(2)Brucellosis
(3)Sarcoidosis
(4)Visceral leish maniasis
(5)Malaria
(6)Bartonellosis
(7) Histoplasmosis
(8)Toxoplasmosis
(9)Schistosomiasis
(10) Trypanosomiasis(11)Relapsing fever
(12)Melioidosis and Glanders