Beijing residents are troubled by fleas. How can fleas still exist in the 21st century?

Some time ago, Beijing Daily reported that fleas appeared in Rongzunbao Community in Chaoyang District, Beijing. Not just one, but a large group of them, biting residents so much that their legs were covered with lumps.

Related news, image source: Weibo

In recent days, some netizens have revealed that residents of Hongmiao Beili Community in Chaoyang District are troubled by fleas.

Fleas? Aren't those as old as spicy snacks, cassettes, and tin frogs?

People born in the 80s and 90s may have heard of them, but people born in the 00s probably only have the chance to learn about them when they look them up in the dictionary. Why are they making a "comeback"?

01

What does the flea population depend on?

In junior high school biology textbooks, organisms are divided into six levels: phylum, class, order, family, genus, and species. For example, if you want to understand a person, you usually first ask him what country he is from, then what his race is, and then ask him about his province, city, neighborhood, and house number.

The seemingly inconspicuous fleas actually have a very large family: more than 2,500 species (subspecies) have been discovered worldwide, and there are more than 650 species (subspecies) in China alone.

Fleas, Image source: CDC

These fleas with different postures have two common characteristics.

First, their life cycle includes four stages: egg, larva, pupa, and adult. Eggs are insect eggs. When they encounter suitable temperature and humidity, they hatch into larvae. Larvae look a bit like maggots and prefer dark and humid environments. After two molts, they enter the "cocooning" stage. The duration of the pupal stage varies. If the conditions are not suitable, it may be a year. If the conditions are suitable, it only takes 1 to 2 weeks. Finally, under external stimulation, such as air vibration, animal movement, and temperature rise, the pupa will emerge and become the fleas we are familiar with.

The life cycle of fleas. Image source: onlynaturalpet.com

Second, all fleas suck blood. Only female mosquitoes suck blood, but fleas, regardless of gender, suck blood several times a day, each time for 2 to 10 minutes. They suck blood many times, for a long time, and they defecate while sucking blood, so it is easy to spread diseases.

The number of fleas is closely related to the external environment.

First of all, the local environment. Generally speaking, warm, humid and dark environments are prone to breeding fleas.

Secondly, the number of wild animals (dogs, cats, rodents, marmots, etc.) is related to the number of fleas.

Finally, it is the weather. Different fleas are different. For example, the common human fleas in the north are more common in summer, while the Xie's mountain fleas in the western region are most common in autumn.

02

What can fleas do?

Some readers may disagree with this, thinking, "Fleas are so small, how can they cause any serious illness?"

Yes, and there are more than one. Fleas can spread plague and endemic typhus in serious cases, and cause insect bite dermatitis in mild cases. We will focus on plague and insect bite dermatitis.

Diseases that fleas can cause, Image source: self-made by the author

As living conditions improve, plague, like many diseases, has gradually faded from our horizons. However, sporadic plague infections still occur occasionally in North China, Northeast China, and Northwest China. For example, in November 2019, a case was reported in Ulanqab City.

Related news, image source: China Center for Disease Control and Prevention

Plague is caused by Yersinia pestis and there are two ways of transmission. One is contact with wild animals carrying the bacteria, such as rats and marmots; the other is being bitten by fleas carrying the bacteria. The bacteria will block the flea's stomach, so when the flea sucks blood, the blood cannot enter its stomach, but flows back into the animal or human body with the bacteria, causing infection.

Insect bite dermatitis is a skin inflammation caused by mosquito bites. When fleas suck blood, they bite the skin and secrete some saliva. As a result, needle-sized bleeding spots will appear on the skin surface, and the surrounding areas will be slightly red and raised, forming maculopapular rashes, which appear in groups and patches. If you are allergic to flea saliva, you may also develop blisters and erythema. In severe cases, you may even experience anaphylactic shock.

Flea bites, Image source: MedlinePlus

03

How to deal with fleas?

There are two ways to deal with fleas: punishing them before they happen and preventing them from happening again .

How to deal with fleas, Image source: homemade by the author

Prevention is the best way to prevent fleas. The way to prevent fleas lies in the flea's living habits:

First of all, keep the room clean, sweep regularly, open windows for ventilation regularly, and vacuum the kitchen floor regularly. As long as the room is fresh, dry, and free of food residues, it will be difficult for fleas to breed.

Secondly, avoid contact with wild animals. If there are too many stray cats and dogs nearby, you can inform municipal managers and ask them to help deal with them.

Finally, if you have pets, don’t let them run around and bathe them regularly.

What if you have already been bitten by fleas? It depends.

If there are only mild symptoms such as itching, you can use some external antipruritic drugs, such as glucocorticoid cream; if the itching is particularly severe, you can ask the doctor to prescribe some antihistamines; if a serious allergic reaction occurs, don't say anything - go to the hospital as soon as possible.

Let the doctor catch it for you↓↓

References

[1] Zhang Xuejun, Lu Hongguang, Gao Xinghua. Dermatology and Venereology[M]. People's Medical Publishing House, 2013.

[2] Li Yonglong. Human Parasitology[M]. 2008.

[3]Fleas: MedlinePlus Medical Encyclopedia [EB/OL]. MedlinePlus, 2020-10-11. (2020-10-11)[2021-11-13] .https://medlineplus.gov/ency/article/001329.htm.

[4] Health Commission of Inner Mongolia Autonomous Region. A case of bubonic plague confirmed in Siziwang Banner, Inner Mongolia Autonomous Region [EB/OL]. Chinese Center for Disease Control and Prevention, 2019-11-28. (2019-11-28) [2021-11-13]. https://www.chinacdc.cn/jkzt/crb/jl/sy/gzdt/201911/t20191128_207187.html.

[5] Wu Li, Yin Jiaxiang. Overview of the relationship between fleas and environmental factors[J]. Chinese Journal of Vector Biology and Control, : 1–4.

[6] Meng Fengxia, Liu Qiyong. History of flea control and integrated flea control[J]. Chinese Journal of Vector Biology and Control, 2004, (05): 341–343.

END

Author of this article: Zhang Yuhong, associate chief physician of dermatology, Zhengzhou Central Hospital Affiliated to Zhengzhou University.

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Author/Zhao Yanchang

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