The greatest challenge for Veterinarians is differential diagnostics based only on symptoms. It always begins with owners answering to Veterinarian's questions, and based mainly on clinical signs and behavior alterations. To confirm any diagnostic it is mandatory to use laboratory exams, considering that for each symptom it is possible to identify many other infectious and non-infectious diseases. Table 1 shows symptoms and their most frequent infectious causes.

HA--Hemagglutination
IHA--Hemagglutination inhibition
IH--Immunohistochemistry
SN--Serum neutralization
SA--Serum agglutination
MSA--Microscopic serum agglutination
IFA--Indirect Immunofluorescence
IDGA--Immunodiffusion in Agar gel
CNS--Central Nervous System

Diarrhea is a very common symptom and Giardia and Cystoisospora are mostly found in puppies that ingest feces and contaminated water, remaining as an important source of infection for other animals, considering that the ingestion of only 10 Giardia cysts is sufficient to infect and cause diarrhea. Clinical signs could be very severe, but some dogs do not show any symptom. Acute chronic diarrhea is the most common symptom; nonetheless vomit, dehydration, weight loss and abdominal pain may occur. Trophozoites (active form found in gut mucosa) do not survive in the environment, but cysts (infecting form) are resistant to chlorinated water and susceptible to high temperatures and am bone marrow solutions. The incidence of Giardia infection in Brazil ranges from 2-39% at laboratory diagnostic tests considering the most frequently used method (centrifugation-fluctuation with Zinc sulphate). A single negative result at this method is not conclusive, due to the intermittent shedding of cysts, therefore the most indicated recommendation is to obtain 3 fecal samples in alternate days, during one week. ELISA is also being successfully used for Giardia diagnosis.

The most important way to control and prevent infections are: washing and disinfecting environment; treating and cleaning the dogs, considering that cysts can adhere on fur; verify water quality; vaccination; treatments. To avoid reinfection we suggest treating after second vaccine dose, during the primary vaccination schedule.

Jaundice is another important symptom that could indicate several diseases, such as, hepatitis, intoxication, and, although leptospirosis is the first suspect disease remembered by veterinarians, it is not the main symptom. Apathy, anorexia, fever, vomit, diarrhea, mucosal hemorrhages, muscle and abdominal pain, are frequently seen. Serogroup cross reactions occur frequently and previous vaccination schedule must be known, to avoid incorrect diagnosis. Seropositivity in vaccinated dogs is mostly under 1:320 and lasts a few months, but immediately after vaccination dilutions can reach 1:1250. Titers 1:800 or 1:1600 can be considered as disease when vaccination occurred 3 months before and 1:3250 is a confirmed positive result.

All the clinical signs showed at table 1, mainly skin lesions, pyodermitis, demodectic mange, epistaxis, ataxy, renal failure, could be frequently related to Visceral Leishmaniasis. Veterinarians of recently infected regions must be aware and perform diagnostic tests as serology (ELISA) and confirmation at parasitological tests, taking samples from bone marrow and/or lymph nodes. Other tests, including serology by IFA, lymph node or skin samples biopsy for Immunohistochemistry, PCR and culture could be used. The correct diagnostic test, considering many different infectious causes, is surely the best way to save animals live and to conserve their owners as your client. As Brazil can be considered an endemic country for leishmaniasis and clinical signs are similar to many other diseases, it is important for all Veterinarians to include serological test of any suspect dog, considering that it is a zoonosis. Vaccines are licensed at the Ministry of Agriculture and are being used by Brazilian Veterinarians. The use of canine vaccines is considered the main control method for Visceral Leishmaniasis, according to Dye (1996).

References

1.  Olson ME, Ceri H, Morck DW. Guardia vaccination. Parasitology Today, 2000. May;16(5);177-218

2.  Levett PN. Leptospirosis. Clinical Microbiology Reviews, vol.14,n.2,p.296-326, Apr.2001

3.  Overmann J. Canine leptospirosis: Interpreting titers. Veterinary Diagnostic laboratory, University of Minnesota,2007.

4.  Whol JS. Canine leptospirosis. Comp. on Cont. Educ. for the Pract. Vet. article #4, v 18, n.11,p1215-1225,1996.

5.  Palatnik-de-Sousa CB, et al. FML vaccine against canine visceral leishmaniasis: from second generation to synthetic vaccine. Expert Review Vaccines 7 (6), p 833-851, 2008.

6.  Dantas-Torres F. Leishmune vaccine: The newest toll for prevention and control of canine visceral leishmaniasis and its potential as a transmission-blocking vaccine. Veterinary Parasitology 141 (2006) 1-8

7.  Dye C. The Logic of visceral leishmaniasis control. Am J. Trop. Med. Hyg. 5512, (1996), p 125-130

8.  Nunes CM. Dog culling and replacement in an endemic area for visceral leishmaniasis in Brazil.