RITM Vet team evaluates possible use of faster, cheaper rabies detection kit

Detecting rabies on animals may now possibly be cheaper and quicker following ongoing evaluation studies on rabies antigen detection kit.

RITM veterinarian and head of the Special Pathogens Laboratory Dr. Catalino Demetria said they found 98.69% sensitivity, 100% specificity, and 98.98% accuracy on the use of rapid immunochromatographic test or RICT in diagnosing animals for rabies.

“When you do a test and the result was positive, most probably the animal is really positive of rabies. But when the result is negative and the records are saying otherwise, that is when you need to reconfirm the samples,” said Dr. Demetria on the importance of conducting lab test for rabies along with the required accomplished interview form, which include data on age of the animal, vaccine history, signs and symptoms observed, and nature of bite on the victim.

Currently, laboratories use direct fluorescent antibody test (FAT) in rabies detection. This method is difficult, costly, time-consuming, and requires trained personnel.

With the RICT detection kit, results could be visible in less than 15 minutes, with the positive test line showing after only around three minutes. It does not also need high cost equipment and highly technical skills, as compared to current available diagnostic tests used in rabies such as virus isolation, microscopy, real time and conventional PCR, rabies tissue culture infection test immunohistochemistry, and the IgG antibody test*.

According to Dr. Demetria, the RICT test can especially be applied in the field conditions and first-line laboratories where resources are limited and rapid diagnosis is required. It could also be an important tool in providing immediate decisions on administration of post exposure prophylaxis.

“Traditional laboratory setup costs millions. As a matter of fact, the microscope for DFAT in a specialized lab for rabies costs one million pesos already, while the conjugate used for rabies detection costs about Php 60,000 – and it’s only good for 300 samples,” said Dr. Demetria.

A rabies detection kit would also come in handy for local laboratory personnel considering that the Philippines has an archipelagic profile where land transportation of samples is rarely an option.

“In the Philippines, elimination of rabies is done island by island or per province. And to say that a province/island is rabies-free, there should be a way to diagnose and confirm absence of human and animal rabies in a locality for three years. RICT is one way to confirm this,” explained Dr. Demetria when asked about possible contribution of the kit to the rabies eradication goal by 2030.

Similar to any diagnostic method, false negative results could still occur due to the sequence of viral infection and distribution in the early stages of infection and in poorly preserved tissue. When this happen, the study still recommends that it undergoes re-confirmation by animal history or other laboratory techniques.

When asked about the future directions of the study, Dr. Demetria said that the team plans to test more samples so that the data could be more conclusive. They are also planning to do the study in suspected human rabies patient.“RITM is the only laboratory in the country that confirms human rabies,” added Dr. Demetria.

An average of one person every nine minutes die of rabies yearly. With over 59,000 deaths globally, rabies continuous to be one of the deadliest preventable diseases. Philippines is among the top ten countries with the highest incidence of rabies, with over 200-300 Filipinos dying each year. Most of these deaths are not laboratory-confirmed.

Celebrating the Rabies Awareness Month this March, the RITM is one with the fight to eradicate rabies by 2030.

* There is no IgM or IgG test available for rabies diagnosis since the patient lives just for around 48 hrs after appearance of symptoms. Antibody tests available are for the detection and measurement of titers after vaccination.

by JA Quinto, Communication and Engagement Office