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Hong Kong environmental issues

How bad is Hong Kong’s summer rat problem?

Everything you need to know about the rodent infestation, from the diseases they carry to what to do if there’s a mouse in your house

PUBLISHED : Wednesday, 18 July, 2018, 3:10pm
UPDATED : Thursday, 19 July, 2018, 8:18pm

Hong Kong residents and pest control experts have been reporting a rampant rodent problem since the beginning of the summer, with an exceptionally long hot spell possibly encouraging the vermin to breed and alter their usual behaviour.

1. Is the rodent infestation serious?

The city’s Food and Environmental Hygiene Department has been using the rodent infestation rate (RIR) for areas under its management since 2000 as an index. The RIR for the second half of 2017 for the city as a whole was 3.5 per cent, down from 4 per cent in 2016. The department said rodent infestation in the city was “not extensive” and “generally under control”. But it also said the RIR might not fully reflect the situation in individual districts.

How the plague swept through Hong Kong

Over the years, there have been occasional media reports about rodent bites. The last case of the plague – a deadly infectious disease linked to rodents and their fleas – reported to the city’s health authorities was in 1929. In 1894, the disease claimed at least 2,500 lives in four months in Hong Kong. Outbreaks of varying seriousness continued to occur up to 1929.

2. What rodents are commonly found in Hong Kong?

Common species in Hong Kong are Rattus norvegicus, also known as the sewer rat, Norway rat or brown rat; Rattus rattus, also called the house rat or roof rat; and Mus musculus, or more commonly, the house mouse. These social and highly adaptable animals are nocturnal and are good climbers and swimmers, especially Rattus rattus. The range of movement is 30 to 50 metres for rats, and five to 10 metres for mice. A rat can consume 15 to 30 grams of food daily. A mouse consumes only three grams of food.

3. What health issues do rodents bring?

Rodents are carriers of viral, rickettsial and bacterial diseases. The causative agents can enter the human body via fleas, ticks and mites, through food or water contaminated by rodent waste, or through rat bites. Common rodent-borne diseases include the plague, urban typhus, spotted fever, scrub typhus, hantavirus infection and rat-bite fever.

4. How do the health authorities tackle rodents?

The Food and Environmental Hygiene Department adopts an integrated approach to rodent prevention and control through cleansing, trapping and use of poison bait based on World Health Organisation guidelines. The department also conducts an annual citywide anti-rodent campaign. This year, additional operations will be conducted in designated target areas for two months.

Hong Kong’s hot weather is forcing rodents up high-rises

Since 2000, the department has been using the RIR and other information to devise anti-rodent measures, though the reliability of such figures has been challenged by pest controllers and lawmakers. The department said there was no internationally adopted rodent infestation index, and its approach took reference from overseas practices while considering local factors. The authorities have also conducted surveys to calculate a rat-flea index.

5. How can the government improve rodent control?

Veteran pest controller Gary Yam Wing-keung said the government should stop wrapping bait in plastic for its half-yearly rodent infestation surveys, as this made it hard for the animals to detect it. The authorities could also consider using better poison bait, and switching to the rodent boxes often deployed by local pest controllers instead of traditional cage traps, which have limited capacity, he said. More inspections could be conducted in alleys to tackle the issue of food remnants dumped there by restaurants.

6. What should I do if there are mice or rats in my home or office?

Gary Yam said glue traps and cage traps can be used but should be placed next to vertical surfaces to take into account the rodents’ movement habits. Keeping a cat may not be a good idea, as some domestic felines have lost interest in rodents, while pet food could also attract the pests. Diseases from rodents might infect cats too. Maintaining good hygiene in the environment is essential.

Five ways cities tried, and sometimes failed, to be rid of rats

The Food and Environmental Hygiene Department provides a 24-hour collection service for caught live rodents at its 2868 0000 hotline. Dead rodents should be sprayed with disinfectant and put in tough plastic before being disposed of.