VMC 311: Systematic Veterinary Bacteriology and Mycology (2+1)

DIAGNOSIS

• It vary with the disease, but usually include unclotted blood for blood smears, affected tissues (such as brain in heart water), paired serum samples for serology are appropriate.
• In Q fever, besides blood, the sputum and less often the urine, may yield the causative agent.
• By Direct microscopy
  Both blood and tissue smears, stains such as Giemsa, Gimenez, Machiavello and Leishman as well as FAT are useful.
• By Isolation and cultivation
  This is often difficult and is not usually necessary for a laboratory diagnosis.
• Guineapigs and mice are useful for primary isolation. Suspected materials are inoculated i/peritoneally and the animals have to be observed for 3-4 weeks for raising their temperature. (Rochalimae quintana will not grow in guinea pigs and mice).

Disease	Diagnosis
Q-fever	Detection of organisms in Giemsa or FAT stained smears from ruminant placentas Inoculation of chicken embryos, guinea pigs and hamsters Paired sera samples for agglutination, CFT and ELISA Allergic test The cattle and horses are inoculated in the lower eyelids with the antigen. After 3-4 days, there is acute swelling of the eyelid in the positive case with rise in temperature.
Canine ehrlichiosis	Giemsa stained blood smears (best at 13th day post infection) - characteristic inclusion in monocytes and neutrophils Serology – indirect FAT
Salmon poisoning	Observation of characteristic fluke eggs in faeces Giemsa, Gimenez or machiavello stained smears of fluid aspirated from lymphnode
Heart water	Giemsa or FAT stained smears from brain tissue Inoculation of susceptible cattle or mice

Weil-felix reaction

• This test was developed by Weil and Felix (1916).
• The weil-felix reaction is a simple and specific agglutination test for the diagnosis of some rickettsial disease.
• The basis of the test is the sharing of an alkali stable carbohydrate antigen by some rickettsiae and by certain strains of Proteus, P.vulgaris OX19 and OX2 and Proteus mirablis OX k. This test is usually done as either tube or rapid slide agglutination test.
• The test is of no value in diagnosis of trench fever and Q fever.

Weil- felix reaction in rickettsial disease

Disease	Agglutination with
	OX 19	OX 2	OX k
Epidemic typhus	+++	±	-
Endemic typhus	+++	±	-
Rocky Mountain spotted fever	++	++	-
Scrub typhus	-	-	+++
Trench fever	-	-	-
Q-fever	-	-	-