**2. Epidemiological records**

#### **2.1 National surveys on human taeniasis/cysticercosis**

Three national surveys on parasitic diseases in humans have been conducted in China until now (**Table 1**). In the first national survey (1988–1992), a total of 1,477,742 individuals from 30 out of 34 provinces in China were investigated, and 2449 individuals from 28 provinces were found to have *Taenia* spp. infections [24]. These data led to an estimation of about 1.3 million cases of *Taenia* spp. infection in the country [25]. The second nationwide survey (2001–2004) conducted in 31 provinces (out of 34 provinces in China) with a total sample size of 356,629 people revealed that 983 people from 12 provinces (38.7%, 12/31) were diagnosed to have *Taenia* spp. infestation [26]. According to these findings, 0.55 million people were infected in total estimation [26].

Taenia solium *Taeniasis and Cysticercosis Prevalence and Control Practice in China DOI: http://dx.doi.org/10.5772/intechopen.110628*

#### **Figure 1.**

*The life cycle and mode of transmission of Taenia solium in humans and pigs. The blue cycle indicates the traditional life cycle of Taenia solium. Humans become infected and the tapeworms colonize in the gut after consuming raw or undercooked pork containing larval tapeworm, the cysticerci that matures into an adult worm in the human small intestine in about 2 months. The worm's eggs or the most distal segments (proglottids) carrying mature eggs are periodically released/detached and subsequently discharged into the environment with human stool. Pigs get infected when they consume infectious eggs (gravid proglottids) in human excrement, food, water, and soil. Both humans and pigs could serve as intermediate hosts, and the embryo (oncosphere) is released after ingestion and migrates through the intestinal mucosa. Later, the larval stages (cysticercus) commonly infest host body organs such as the brain, eyes, subcutaneous tissues, and viscera via the blood circulatory system. Similarly, humans become infected by consuming raw or undercooked pork containing cysticerci that mature into an adult worm in the small intestine in about 2 months. The red dashed cycle represents the rebuilding Theridion solium life cycle. As a result of a structural shift in pig farming from backyard to large-scale intensive pig farming, as well as a toilet revolution aimed at improving sanitary conditions, the transmission of T. solium between humans and pigs has been significantly interrupted, and spread of the disease is being gradually lessened.*


#### **Table 1.**

*National surveys on human taeniasis/cysticercosis in China.*

Likewise, in the third nationwide survey (2014–2015), *Taenia* spp. was found in 1752 people from 12 provinces (38.7%, 12/31) out of 617,441 people under investigation from 31 provinces (out of 34 provinces in China) [27]. Considering the demographic structure in the whole population, a weighted prevalence of 0.06 percent was calculated, implying that 0.37 million people were infected [27].

Three national surveys on human parasitic disease in China revealed a significant decline in human *T. solium* taeniasis/cysticercosis, while recorded cases indicated that *T. solium* cysticercosis was traditionally endemic in northeastern, central, and southwestern China (**Figure 2**). However, infection rates have been high in areas in the southwest of China with poor socioeconomic conditions, particularly in Tibet, Sichuan, and Yunnan [3, 28–30].

#### **2.2 Case summary of human taeniasis/cysticercosis**

There are a variety of human taeniasis/cysticercosis case reports in China. Among them, brain neurocysticercosis (NCC) was the most prevalent (75.87%), followed by subcutaneous infections (11.17%). Several reports have documented mixed infections related to multiple organs, with the brain and subcutaneous cysticercosis being the most common (4.74%) (**Figure 3**).

#### **2.3 Prevalence of human taeniasis/cysticercosis**

The epidemiology of human taeniasis/cysticercosis has been well documented and recorded in the same area for many years (**Figure 4A**). It is observed that the prevalence rates have generally been declining when the prevalence rates for various years in the same location are compared [3, 28, 29]. Analysis of risk factors revealed that the prevalence of human cysticercosis is the highest in areas where sanitation is poor, toilets are lacking, and people traditionally consume raw or under-cooked pork (or viscera) and/or where pig husbandry is substandard [3, 28, 29, 31–33].

#### **2.4 Field prevalence of porcine cysticercosis**

As with human cysticercosis, there were numerous studies on the epidemiology of porcine cysticercosis, which were mostly carried out during the slaughter quarantine. For a comparative analysis of the prevalence rates of the human cysticercosis for different years in the same area, it is found that the prevalence has been significantly declining (**Figure 4B**). Humans are the only natural definitive host for cysticercosis [8], and pigs become infected through consumption of human feces in areas where open human defecation is common, and also through contaminated food, water, and soil [8].
