Application and Comparative Evaluation of Fluorescent Antibody, Immunohistochemistry and Reverse Transcription Polymerase Chain Reaction Tests for the Detection of Rabies Virus Antigen or Nucleic Acid in Brain Samples of Animals Suspected of Rabies in India.

K Nithin Prabhu,Nagendra R Hegde,Shrikrishna Isloor,Doddamane Rathnamma,Sira Abdul Rahman,M L Satyanarayana,B Hanchinal Veeresh,R Sharada,Lekshmi J Das

doi:10.3390/vetsci5010024

Abstract

Accurate and early diagnosis of animal rabies is critical for undertaking public health measures. Whereas the direct fluorescent antibody (DFA) technique is the recommended test, the more convenient, direct rapid immunochemistry test (dRIT), as well as the more sensitive, reverse transcription polymerase chain reaction (RT-PCR), have recently been employed for the laboratory diagnosis of rabies. We compared the three methods on brain samples from domestic (dog, cat, cattle, buffalo, horse, pig and goat) and wild (leopard, wolf and jackal) animals from various parts of India. Of the 257 samples tested, 167 were positive by all the three tests; in addition, 35 of the 36 decomposed samples were positive by RT-PCR. This is the first study in which such large number of animal samples have been subjected to the three tests simultaneously. The results confirm 100% corroboration between DFA and dRIT, buttress the applicability of dRIT in the simple and rapid diagnosis of rabies in animals, and reaffirm the suitability of RT-PCR for samples unfit for testing either by DFA or dRIT.

Highlights

Rabies is an infectious viral disease that is almost always fatal following the onset of clinical symptoms
Some of the samples (n = 101; from Kerala, 8 from Maharashtra, 19 from Punjab, 18 from Tamil Nadu, 5 from Uttar Pradesh) were sourced from other institutions, and were obtained for comparing the different diagnostic tests. These were archived samples that had been collected earlier based on presumptive diagnosis of rabies, and confirmed by direct fluorescent antibody (DFA) at laboratories located in the respective states
Despite an estimated 35% of all the human rabies deaths worldwide occurring in the country [21,22], the disease is not notifiable in India

Summary

Introduction

Rabies is an infectious viral disease that is almost always fatal following the onset of clinical symptoms. Given the importance of the spread of rabies to humans by canids and other carnivores, the protracted incubation period, the often delayed appearance of typical symptoms, rapid and accurate diagnosis of rabies in animals is critical for prognostication, and for initiating and implementing post-exposure prophylaxis, infection-control strategies and public health measures. The direct fluorescent antibody (DFA) test is the gold standard [9,10] This test detects the presence of rabies virus antigen in infected tissues, in the brain. Enzyme immunoassays, such as rapid rabies enzyme immunodiagnosis (RREID), are as sensitive and specific as FAT, and can be applied to partially decomposed samples; brain tissues need to be homogenized, resulting in a potential exposure hazard to laboratory personnel. DRIT has been increasingly employed for the laboratory diagnosis of rabies, owing to its simplicity [11,12,13]

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Conclusion