Molecular characterization of Caprine Arthritis Encephalitis Virus (CAEV), can now be used as a tool in the control and eradication of the virus that causes ill-effect on goats.

“This is significant," said lead researcher Ryan Bismark C. Padiernos of the Animal Health Unit of Philippine Carabao Center (PCC). “It was the first in the country in so far as the genetic characteristics of CAEV is concerned,” he added.

It can help in developing detection kit specific for local strain of CAEV and in responding to the emerging issues of small ruminant lentiviruses in the country, he further said.

The study “Molecular Characterization of Gag Gene of Caprine Arthritis Encephalitis Virus of Goats Present in the Philippines” was funded by the Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD).

Previous studies indicated that CAEV is a retroviral infection of goats that is typically transmitted through ingestion of virus-infected colostrum or milk from infected does and horizontal transmission through respiratory exudates. Currently, there is no specific treatment or commercially available vaccines against CAEV. Infection is usually controlled by eradication of infected goats.

Big losses in the goat industry in the country, it said, are attributed to CAEV. Thus, the Department of Agriculture classified this infection as an emerging disease, making CAEV a potential threat to the goat industry.

In the study of Padiernos’ team, goat blood samples were collected from (big) farms with history of CAEV infection and from backyard farms that are not exposed to the virus. These farms were described as having sporadic clinical cases of carpal arthritis, mastitis and emaciation among breeding stocks. Those considered backyard farms were chosen for the collection of samples because of the assumption that CAEV infection might be present among pure native goats.

Using nested PCR and designed set of primers for amplification, the researchers were able to detect CAEV in the gag gene, which is the highly conserved region of the virus.  

Result of the study showed that only 3.77% of CAEV samples that were positive to β-actin PCR were successfully amplified.

The amplified gag gene was sent to First Base Malaysia for DNA sequencing. Sequence data analysis and homology analysis were done using the Basic Local Alignment Search Tool (BLAST) search of the National Center for Biotechnology Information (NCBI).

BLAST is an algorithm for comparing primary biological sequence information, such as the amino-acid sequences of different proteins or the nucleotides of DNA sequences.

Multiple sequence alignment and phylogenetic trees were generated using the Mega Evolutionary Genetics Analysis Version 5 (MEGA 5).

MEGA is an integrated tool for conducting automatic and manual sequence alignment, inferring phylogenetic trees, mining web-based databases, estimating rates of molecular evolution, and testing evolutionary hypotheses.

DNA sequencing analysis showed homology of 86%-93% between Philippine CAEV and 86%-91% between other known CAEV genome registered in GenBank, respectively. However, the study cannot conclude the over-all diversity of Philippine CAEV due to the reason that only small number of animals showed positive result of the virus.

It was also found out that there are 17 amino acid deletions in the Philippine CAEV isolate that can indicate a new strain of virus based on the amino acid sequence alignment conducted. This new strain may have been already present in the country even before the start of goat importation.

The variable region in the amino acid sequence was also detected similar to the variable sequence of Canadian CAEV sequence based on researches done in the past.

The study further confirmed that the Philippine CAEV isolate shows 90% identical with CAEV-Co strain from USA. It proved the importance of the need to understand the genetic characteristic and diversity in epidemiological studies and in tracing the origin and evolution of this disease.

Also achieved in the study is the necessity of establishing a caprinelentivirus phylogeny for future molecular epidemiology studies to serve as reference for the development of an improved molecular diagnostic test. This test can validate serologic assay for monitoring and eradicating CAEV in the country, it said.

The researchers also recommended the development of a diagnostic tool to identify infected goats prone to local strains of CAEV.

Padiernos was awarded the “Best Paper for Completed Research” award for this particular study in the recent PCC’s R&D In-House Review. The members of his team were Dr. Michelle M. Balbin, Arman M. Parayao, and Dr. Claro N. Mingala.