There have been scares that rats used in school laboratory dissections could infect students with the potentially fatal rabies virus.

Hong Kong’s agriculture and fisheries department says the import of rats must be accompanied by a rabies-free quarantine certificate issued by the country of origin.

But Hong Kong suppliers say unscrupulous dealers smuggle rats across the border from China, where rabies is rife in some areas, and sell them at two-thirds the market price, exposing children to risk.

Each A-level biology student in Hong Kong has to dissect at least 10 white rats a year as part of the preparation for university entrance. At least 50,000 white rats are used each year by A-level students and more by undergraduates.

While no cases have yet been detected of biology students being infected, controls have been stepped up by both schools and the Agriculture and Fisheries Department to inspect rats coming over the border, and schools are being urged to check up that their suppliers have the right documentation.

Meanwhile in India, students are complaining they are “nauseated and traumatised” as a result of compulsory dissections of frogs and rats in science class.

Former environment minister Maneka Gandhi is planning to move a petition in the Delhi High Court to stop compulsory dissections in science classes. Dissections leave some children in severe shock, Mrs Gandhi said after receiving letters from more than 5,000 students.

Some 20 million frogs are dissected a year in the country and the practice is compulsory for science students aged 14 and above. She said children were being forced to perform dissections against their will and some even decide to drop biology because of it.