The Asian elephant calf named Mac at the Houston Zoo began treatment for elephant herpes virus Sunday.

"Houston Zoo elephant keepers alerted our veterinarians this morning when they saw early indications that Mac was exhibiting symptoms of lethargy and diminished appetite," said Houston Zoo spokesman Brian Hill.

Mac was born at the Houston Zoo two years ago.

According to Hill, veterinarians at the zoo immediately began administering Famciclovir to the calf. Famicicolovir is an antiviral medication that has shown some limited success in past elephant herpes cases.

"Mac is receiving round-the-clock care from our vets and keepers that he knows and trusts. His mother Shanti and his aunt Methai are nearby," said Hill.

Zoo veterinary staff is also consulting with national experts recognized in the field of the elephant herpes virus, Hill said.

Many questions about the disease remain unanswered. With funding from the Houston Zoo, the National Institutes of Health, the National Zoo and other institutions, researchers are studying the DNA of the virus in an effort to develop an antibody profile. Results could help determine how to treat the disease.