I. What Are Disease Vectors?
Disease vectors are animals that directly or indirectly transmit diseases that primarily affect humans, posing significant risks to public health. Common vectors include rodents, mosquitoes, cockroaches, and flies. Such vectors spread pathogens quickly and can trigger epidemics, making them a serious concern for public health.
II. Common Rodent Species
Rodents are gnawing mammals and rank among the "Four Pests" targeted in vector control. China hosts about 145 rodent species, representing roughly 34 percent of its mammal diversity. While species composition varies by region, the house mouse and the brown rat are commonly found throughout the country.
(I) House Mouse: This kind of small rodent measures 60 to 90 mm in body length, with a tail that is nearly equal to or slightly shorter than its body. A key identifying feature is a single distinct notch on the inner surface of the upper incisors. Its back exhibits fur in shades of gray-brown to dark brown, contrasting with a gray-yellow underside where the hairs are gray at the base and yellow at the tip.
(II) Brown Rat: Large and stout in build, with a tail shorter than the body. Its ears are too short and fleshy to cover the eyes when pulled forward. Its hind feet are robust. The dorsal fur varies from tan-brown to gray-brown, with a dark gray base and brown tips. The mid-back is interspersed with abundant entirely black hairs, giving it a noticeably darker shade than the sides. The underparts are grayish-white, with hairs gray at the base and white at the tip. The upper side of the feet is covered in white hair, and the tail is distinctly bicolored: dark brown above and grayish-white below.
III. Hazards Posed by Rodent Vectors
Rodents act as natural reservoirs and transmitters of a multitude of deadly pathogens. They are capable of spreading human diseases such as plague, epidemic hemorrhagic fever, leptospirosis, and murine typhus, presenting a severe challenge to global public health.
Rodent-borne diseases are primarily transmitted through three routes: firstly, via ectoparasites, where pathogens are spread to humans through the bites of external parasites that have infested infected rodents; secondly, through contamination, as rodents carrying pathogenic microorganisms contaminate food or water sources with their urine, feces, or saliva, leading to human infection upon ingestion; and thirdly, by direct contact, through bites from infected rodents or direct exposure to pathogens.
(I) Plague: A quarantinable disease and a Class A notifiable infectious disease in China. Caused by the yersinia pestis,this virulent disease manifests with a rapid onset, high contagiousness, and a significant mortality rate. The incubation period is generally short, ranging from 1 to 6 days (most commonly 2 to 3 days, with rare cases extending to 8 or 9 days). Patients across all clinical forms of plague commonly present with a sudden onset ofsharp rise in temperature to 39-41°C, accompanied by chills, a sustained high fever, severe headache and may include symptoms such as central nervous system-induced vomiting, tachypnea, tachycardia, and decreased blood pressure. In severe cases, patients can develop a marked drop in blood pressure, impaired consciousness, or delirium even in the early stages of the disease.
(II) Epidemic Hemorrhagic Fever: Also known as hemorrhagic fever with renal syndrome, the epidemic hemorrhagic fever is a notifiable infectious disease.It is caused by the Hantavirus and is classified as a natural focal disease. The illness is transmitted through contact with rodent excreta or secretions, direct exposure to rodents, or bites from berry bugs. Its clinical manifestations are marked by headache, orbital pain, and lumbar pain,as well as flushing of the face, neck, and chest, along with renal impairment.
(III) Leptospirosis: This disease is caused by pathogenic leptospires, which are primarily spread through water or soil contaminated with rodent urine. Symptoms include high fever, muscle pain, and conjunctival injection. In severe cases, patients may develop jaundice, kidney failure, and hemorrhagic tendencies.
IV. Prevention of Rodent-Borne Diseases
(I) Implement scientific rodent control. Deploy adhesive trays, snap traps, or rodenticide baits in areas with rodent activity. Baits should be placed in concealed locations or directly into burrows. Inspect and seal all potential entry points to prevent rodent access, and enhance structural barriers against infestation.
(II) Maintain environmental hygiene. Improve sanitation by regularly clearing away garbage, stagnant water, clutter, and accumulated waste. This reduces potential rodent habitats and eliminates their food sources.
(III) Strengthen food safety practices. Store food items securely, ensure they are thoroughly cooked, and keep raw and cooked foods separated. Regularly sanitize eating utensils to prevent contamination by rodent excreta.
(IV) Adopt personal protective measures. During outdoor work, wear long sleeves and trousers, and apply insect repellent to exposed skin. Avoid prolonged walking through wooded areas or sitting and lying on grass to minimize bites from fleas, mites, and ticks.
V. The Role of Customs in Border Security and Public Health Protection
Customs authorities implement the following key strategies to secure national borders against health threats. Firstly, conducting rigorous baseline vector surveillance. Customs follows the "Four Fixed" principle, namely deploying fixed personnel, at fixed times, in fixed habitats, using fixed methods, to monitor rodent density in port areas. This is achieved through systematic trapping methods using snap traps and live cages.
Secondly, preventing the introduction of vectors. Comprehensive surveillance is conducted on all inbound conveyances (including vessels, aircraft, and trains), containers, cargo, express parcels, and postal packagesto detect and prevent the introduction of invasive vectors. Intercepted rodents are promptly transferred to laboratories for species identification and pathogen screening. Customs then guides relevant entities in implementing prescribed disinfection procedures, effectively eliminating the risk of importation of rodents and the diseases they transmit.
(by an author fromTianjin Customs)
Disclaimer：The above content is translated from Chinese version of China Inspection and Quarantine Times. The China Inspection and Quarantine Times version shall prevail.
