Evaluation of Direct Rapid Immunohistochemical Test (DRIT) of Canis lupus familiaris Hippocampal Touch Impression Smears Using a Monospecific Polyclonal Antibody for Rabies Virus Detection

Mary Jasmin C. Ang,1 Daria Llenaresas–Manalo,2 Blanca Jarilla,3 Laarni Tuason,2
Eleonor Avenido,Catalino Demetria,2 Plebeian Medina,2 Beatriz Quiambao,4
Luz Acosta,3 Satoshi Inoue5 and Ma. Amelita Estacio1

1 Department of Basic Veterinary Sciences, College of Veterinary Medicine,
University of the Philippines Los Baños
2 Veterinary Research Department, Research Institute for Tropical Medicine, Philippines
3 Immunology Department, Research Institute for Tropical Medicine, Philippines
4 Clinical Research Division, Research Institute for Tropical Medicine, Philippines
5 National Institute for Infectious Disease, Tokyo, Japan


Background. Rabies is an important zoonotic disease that needs to be eradicated worldwide. It is still prevalent in the Philippines, thus development of a relatively affordable but still accurate and rapid post-mortem detection test for the virus is desired, especially in regional laboratories.

Methods. The study evaluated the Direct Rapid Immunohistochemical Testing (DRIT) of hippocampal touch impressions of suspected rabid Canis lupus familiaris using monospecific N protein polyclonal antibody developed by the Research Institute for Tropical Medicine (RITM). One hundred sixty (160) acetone-fixed hippocampal touch impressions were subjected to DRIT.

Results. One hundred thirteen (70.6%) out of 160 samples tested positive for rabies viral antigen (RVA) and 47 (29.4%) out of 160 samples tested negative for RVA. No false positive and false negative result were obtained. The results agree with the gold standard, dFAT.

Conclusion. DRIT was able to detect low to high concentrations of RVA in the hippocampal touch impressions based on the grading distribution. DRIT had 100% sensitivity, specificity and over-all accuracy using monospecific polyclonal antibodies, which suggests its use as a more affordable alternative to the gold standard dFAT.

Key Words: rabies, immunohistochemistry, touch impressions, monospecific polyclonal antibodies, dFAT