Sometimes, a routine diagnostic work-up brings an unexpected result.
A dog was presented to AVCI with non-pruritic hair loss that had been present for several months. On examination, we also noticed a mild opacity of the cornea.
Because chronic alopecia can have many possible causes, we started with an initial work-up that included CBC, trichogram, skin scraping, ALT, T4 and cortisol. We also included a Leishmania antibody rapid test.
CBC, ALT and T4 were within normal limits. The trichogram showed numerous fungal elements consistent with dermatophytosis, while cortisol was low.
Then came the unexpected finding:
The Leishmania antibody test was positive.
Because canine leishmaniasis would be an unusual finding in the Philippines, we repeated the antibody test. The second test was positive again.
We palpated the peripheral lymph nodes and found no obvious enlargement. Nevertheless, we proceeded with a fine-needle aspiration of a lymph node. On microscopic examination, a few structures raised suspicion for Leishmania, although the findings were not sufficiently definitive to confirm the organism by cytology alone.
For now, this remains a suspected — not confirmed — case of canine leishmaniasis.
A positive rapid antibody test tells us that the possibility deserves further investigation, but serology alone — particularly in a country where the disease is not considered endemic — is not enough to establish a definitive diagnosis. Ideally, confirmation would include quantitative serology and a validated Leishmania PCR through a reference laboratory, preferably using an appropriate tissue sample. Identification of the Leishmania species would also be valuable.
What makes the finding especially interesting is its geography.
Canine leishmaniasis is most commonly associated with regions where Leishmania and competent phlebotomine sand-fly vectors circulate. The Philippines is not currently considered an endemic area for canine leishmaniasis. However, previous research has already detected Leishmania antibodies in a dog sampled in the Philippines, showing that unusual findings such as this cannot simply be dismissed.
Sand flies are also present in the Philippines, although local transmission of the Leishmania species responsible for most canine disease has not been established.
Infectious diseases do not always remain within the geographic boundaries where we traditionally expect to find them. Dogs travel, animals are imported and relocated, infections may occasionally be transmitted through non-vector routes, and the distribution of vectors themselves can change over time. International movement of dogs is recognized as one way Leishmania infantum can be introduced into non-endemic areas.
At the same time, one suspected case does not mean that canine leishmaniasis is now circulating in the Philippines. Determining the dog’s place of birth, travel and importation history, ancestry and other possible exposures — and obtaining confirmatory testing — will be important before drawing any epidemiological conclusions.
This case is a reminder of an important part of veterinary medicine:
Keep an open differential. Investigate unexpected findings. Repeat unusual results. And let the evidence lead the diagnosis.
For now, AVCI is documenting this as a suspected case of canine leishmaniasis pending further confirmation.
