Geospatial Distribution of Toxoplasmosis Prevalence among Livestock, Pets and Humans in China, 1984-2020

Yajing Su General Hospital of Ningxia Medical University Xia Qiao General Hospital of Ningxia Medical University Wei Jia General Hospital of Ningxia Medical University Pengtao Wang General Hospital of Ningxia Medical University Yuting Kang General hospital of Ningxia Medical University Ningai Yang General Hospital of Ningxia Medical University Zhijun Zhao (  937000560@qq.com ) General Hospital of Ningxia Medical University


Background
Toxoplasmosis one of the world's most common parasitic zoonoses, caused by the obligate apicomplexan intracellular protozoan Toxoplasma gondii (T. gondii). Infections occur among most genera of warm-blooded animal species and humans with a complex life cycle and pathogenic mechanism. About 30-50% of the global human population is estimated to be chronically infected with this parasite [1]. Whilst the infections are generally either asymptomatic or develop mild symptoms that are self-limited, in some immunocompromised individuals and developing fetuses T. gondii can cause hydrocephalus, chorioretinitis and even death. Hence, the prevalence of T. gondii makes it one of the most damaging zoonotic diseases in the world [2][3].
Country-speci c environmental conditions, eating habits, hygiene, and host susceptibility all contribute to global differences in the prevalence of toxoplasmosis in humans, with previous studies have reported country-speci c prevalence rates of 6.7% in Korea; 12.3% in China; 46.0% in Tanzania; 61.0% in France and 84.5% in Brazil [4][5]. Worldwide, serological studies in livestock revealed that the average T. gondii prevalence is 14.0% in cattle; 27.0% in goats; 66.0% in sheep; and 25.0% in pigs. For 2000-2017, the overall prevalence of T. gondii in livestock in China has been estimated to be 9.1% in cattle and yaks, 11.8% in sheep,17.6% in goats, and 32.9% in swines [3].
Toxoplasmosis has a complex epidemiology being transmitted by vertical and horizontal. Vertical transmission of infection from mother to fetus through the placenta during pregnancy. Horizontal transmission of T. gondii is even more common than congenital, which occurs primarily via ingestion of water, soil and crops contaminated with oocysts or consumption of undercooked/raw meat from livestock (e.g. cattle, sheep and swine) containing cyst-stage bradyzoites [6][7][8]. Regrettably, T. gondii infection cannot be detected by routine meat inspection, and there has been relatively little emphasis on the prevention in the food chain. Meat of infected animals is presumed to constitute a major source of human infection [8].
On the other hand, contaminated pet cats and dogs can also transmit toxoplasmosis to humans. This transmission is generally complex, requiring close contact with pets or their excretions and frequently violating hand hygiene procedures [9]. Notably, cats and other felidae, considered the single de nitive host of T. gondii, are able to excrete oocysts. The oocysts is an environmentally resistant life cycle stage from infected cat faeces, which can remaining infectious for periods up to 18 months or longer and transmitting the infection when ingested orally [10].
Geographic information system (GIS) covers iconology, geographic information science and computer science, used for inputting, storing, managing, displaying and analyzing geographic or spatial data. GIS have been become an essential component of modern disease surveillance systems [11][12].
Investigation using GIS technologies coupled with spatial analysis, provide an important method of establishing a prompt and precise understanding of local data on disease spread, which can help us understand where disease and illness spread and how they may be minimized or stopped. Previous research on toxoplasmosis of livestock and humans has identi ed high-risk geographical areas; however, no study has assessed the prevalence and geospatial distribution among livestock, pets and humans of toxoplasmosis in China using a large population-based data. Here, we aimed to identify the epidemiology and geospatial distribution of toxoplasmosis among livestock (sheep and goats, swines, cattle and yaks), pets (cats, dogs) and humans in China from 1984-2020 using GIS technologies in order to provide suggestions on the prevention and control of this foodborne pathogen.

Data collection
To gather all epidemiological data of toxoplasmosis in China from articles that are published in English and Chinese covering a period from January 1984 to December 2020, PubMed, China National Knowledge Infrastructure (CNKI) and Baidu Scholar databases were searched using the keywords that included "toxoplasmosis, China" or "Toxoplasma gondii, China". Results were then checked for duplicates in the same research group, incomplete original data were reviewed in order to exclude all inadequate articles. Furthermore, the seroprevalence of T. gondii researches was limited to the detection of speci c anti-toxoplasma immunoglobulin IgG in serum, which include indirect hemagglutination (IHA), enzymelinked immunoabsorbent assay (ELISA), and modi ed agglutination test (MAT). Each report was used to extract information on the survey dates, locations (geo-coded to provide a longitude and latitude) of the survey cities, infected number, examined number, publication time and other information.

Spatial orientation and expression
To identify the spatial attribute information of the survey cities, the global positioning system (GPS) (http://www.toolzl.com/tools/gps.html) was used to obtain the latitude and longitude coordinates of each survey city. Meanwhile, we used the longitude and latitude coordinates of provincial capitals for the survey sites only introduced to the survey provinces. ArcGIS 10.2 geographic information system was used to map the geospatial distribution of toxoplasmosis prevalence in China. All the data collected were processed geographically. ArcGIS 10.2 was then used to match the venue of the survey cities with the geographic locations. The administrative map was sourced from Chinese Academy of Sciences Resource and Environment Science Data Center (http://www.resdc.cn/).

Statistical analysis
For prevalence estimates, T. gondii for each survey city was estimated as: number of infected hosts/number of sampled hosts × 100, using Excel software. The results are presented as adjusted rate ratios with 95% con dence intervals (CI).

Results
Geospatial distribution of livestock exposed to T. gondii in China Geospatial distribution of sheep and goats exposed to T. gondii Small ruminants are intermediate hosts of T. gondii, which are highly susceptible to T. gondii and, chronically infectious for life. It is believed that the parasite is a major cause of abortion and neonatal mortality in sheep and goats, resulting in economic loss [13][14]. Furthermore, consumption of raw or undercooked meat from these animals has been regarded as a major route of T. gondii transmission to humans, especially in countries and regions where mutton and beef is regularly eaten [15]. According to the epidemiological data of toxoplasmosis in administrative districts, a map showing geospatial distribution of T. gondii for sheep and goats was generated ( Fig. 1   Geospatial distribution of cattle and yaks exposed to T. gondii Beef and dairy products are widely consumed by humans worldwide, which observed from relevant statistics that the annual consumption of beef in China was > 8 million tons in 2016 and the consumption of dairy products was 40-43 million tons in 2014 [16]. Yak is an iconic species of the Qinghai-Tibet Plateau and, China has 1.3 million yaks accounting for 90% of the world's yak population [17]. It has been reported that isolating T. gondii from seropositive cattle were often unsuccessful, however Dubey JP [18] showed that viable tissue cysts can remain in cattle for up to 1 191 days. Hence, the contaminated cattle and yaks may be an important source for T. gondii transmitted to other animals and humans in China [14]. The geospatial distribution of toxoplasmosis in cattle and yaks in China is shown in Fig. 1 1 and Table 2). Geospatial distribution of swines exposed to T. gondii China is the world's largest pork consumer, as well as the world's largest pork producer with nearly 50% of the world's total production. Swines exposed to T. gondii play an important role as a source of infection for humans [18][19]. The epidemiological data and spatial distribution of T. gondii are presented in Fig. 1 and Table 3 1 and Table 3).  Fig. 1 and Table 4. Moreover, districts Anhui, Jiangxi, Hainan, Shaanxi, Qinghai, Xizang, Tianjin, Taiwan, Hong Kong, and Macao haven't yet been inspected on epidemiological of toxoplasmosis in cats ( Fig. 1 and Table 4). Geospatial distribution of dogs exposed to T. gondii The dog, an intermediate host for T. gondii, may play an instrumental role in mechanically transmitting toxoplasma infection to humans, occurring from dogs via their body surface, mouth and feet [21]. The geographical distribution map of epidemiology of toxoplasmosis among dogs in China is illustrated in Fig. 1 1 and Table 5). Geospatial distribution of humans exposed to T. gondii T. gondii is widely prevalent in China, and its prevalence rate varies widely throughout the country. Humans can acquire the parasite through consumption of undercooked/raw meat infected by T. gondii. In fact, eating raw or undercooked meat have, respectively, 1.2-1.3 times the risk and 1.7-3.0 times the odds of T. gondii infection compared to those who thoroughly cook meat [22]. The geographical distribution map of epidemiology of toxoplasmosis in humans in China is illustrated in Fig. 1 Fig. 1 and Table 6). Moreover, district Macao had no epidemiological data of toxoplasmosis in humans.

Discussion
Toxoplasmosis is the most widespread zoonosis and a signi cant public health problem. Its prevalence varies depends on many factors, including geographical status, climate, environmental in uence, living conditions, age ,eating habits and life style [4]. This zoonosis was studied over the last three decades in China, demonstrating that the epidemiological cycle of T. gondii is very well maintained in this region. Although many seroprevalence studies have been performed in humans and animals in China, data on the geospatial distribution of T. gondii in humans and animals are extremely scarce. For these reasons, this study is innovative because it collected the data on T. gondii infection in livestock, pets and humans from China, and showing the geographical distribution map of epidemiology of toxoplasmosis in a period of thirty years.
Livestock accounts for 60% of the mammals worldwide and is mostly used for meat production, milk and dairy products. Consumption of meat containing viable T. gondii tissue cysts is regarded as important sources of human infection by T. gondii [23]. Among livestock, T. gondii has been found more prevalent in sheep, goats and pigs, than in cattle [4]. Sheep and goats are perceived as biological indicators for the contamination of the environment with sporulated oocysts of T. gondii, because they usually opt for grasses closer to the ground or leaves of shrubs [24][25]. In the present work, the seroprevalence of toxoplasmosis among sheep and goats ranged from 3.98-43.02% in China. Similar work has been published by Dima El Safadi [26] who have worked on the same animal species of North Lebanon, reported that the prevalence of T. gondii infection in 42% of sheep and 34% of goats. Moreover, M Sharif [27] had reported a prevalence of 31% for T. gondii infection in Iran, which was in the same range as the prevalence of infection in this study. Spatial investigations demonstrated variation in seroprevalence of infection in sheep and goats between different regions in China. The prevalence of toxoplasmosis were greater in districts Chongqing, Zhejiang, Beijing and Hubei, because maybe of the climatic conditions are adequate for the sporulation of T. gondii oocysts, due to the hot and humid climate.
Infection with T. gondii is very common in swine. Raw and undercooked meat accounts for 30-63% of T. gondii infections in humans, and according to the prevalence estimates of T. gondii in meat producing animals/meats, pork consumption was estimated to account for 12-15% of T. gondii infections in humans [28]. We further analyzed seroprevalence of T. gondii in swines. The results showed that seroprevalence was ranged from 10.45-66.47%, a higher than those reported in Mexico (8.9%) and Canada (9.4%) [5]. Furthermore, T. gondii is widely prevalent in swines in most areas of China, which may be related to the oocysts from cats or from soil, water, feed; infected rodents and oocysts from kitchen garbage.
Although greater resistance to the T. gondii has been reported in cattle, in the present study the seroprevalence of toxoplasmosis ranged from 0.75-30.34% from cattle and yaks in China. This is in accordance with Tonouhewa [29] who reported that the lowest prevalence rate of T. gondii infections in cattle than in swine and sheep. In cattle, higher prevalence (36.6 and 50%, respectively) had been reported in Colombia and Northern Portugal, and lower seroprevalence rates had been covered in Brazil and Switzerland (2 and 3.8%, respectively) [30]. Moreover, the prevalence in cattle and yaks were higher in Guizhou, Zhejiang, Chongqing, Hunan and, especially Tibet. Tibet has the highest average elevation on earth and, as the representative livestock of Tibet are economically important domestic animals to local herdsmen. To our knowledge, yaks have more chances to ingest T.gondii oocysts through the fecal-oral route, because of free-grazing in the pasture and living together with other wild and domesticated animals. Previously, Kun Li [31] had suggested that the seroprevalence of yaks in the plateau were 21.7% during 2012-2013 that is similar to our results.
Toxoplasmosis, in addition, is also a health problem in pets such as cats and dogs. In cats, the seroprevalence of T. gondii (2.50-60.00%) in the present study was higher than those reported in other studies in Korea (1.6-6.0%) and Japan (5.4-8.7%). Moreover, in Spain, the positivity of T.gondii in cats reported was 27.2%, in the Poland, 68.1% was antibody-positive, and 87.72% of cats had antibodies in Ethiopia. A study performed in mainland China, showed a 24.5% seroprevalence of T.gondii in cats from 1991 to 2015 [32][33].
On the other hand, seroprevalence in dogs has been found in many studies conducted in different parts of the world including those conducted in Mexico (67.3%), Brazil (69.8%), Sweden (23%), Pakistan (28.43%) and Thailand (9%) [34]. Our results revealed that the seroprevalence of T. gondii has ranged from 0.56-27.65% among dogs in China. A previous study had reported a seroprevalence of 1.9% among dogs in Japan in the period 2009-2011 [32]. Cats had higher seroprevalences than dogs, may re ect that cats are better hunters of rodents and small birds than dogs and thus have higher opportunity to be infected with T. gondii.
T. gondii varies greatly between countries and even within different regions of the same country in which may be due to the distribution of the infection source, cultural practices, or hygiene habits. The overall seroprevalence of T.gondii in humans in China from 2000 to 2017 was 8.2%, much lower than the prevalence recorded in Brazil (84.5%), France (61.0%), and United States (38.0%) [5]. The present results indicate that the prevalence of T. gondii infection in humans ranged from 0.72-23.41% in China. The seroprevalence of toxoplasmosis in humans at the level of geographical regions showed the highest infection rate in Taiwan, and the lowest in Beijing. GIS maps, as critical tools in tracking and combating contagion, has been shown to be very effective to investigate the spatial distribution of disease outcomes, the graphical analysis of epidemiological indicators, the associated social factors, and environmental exposures. Indeed, the functions of GIS also plays a very important role in understanding of the new disease source, dynamics and epidemiology, early warning and forecasting of epidemic diseases and evaluating the effectiveness of disease in the prevention [35]. Haroon Ahmed used the GIS system to study the toxoplasmosis in sheep and goats in North-Eastern Region of Pakistan. They found that widespread environmental contamination with T. gondii oocysts, and undercooked meat of infected small ruminants could be a potentially important source of T. gondii infection [1]. Similar work has been conducted at Serbia to investigate the spatial epidemiology of T. gondii in goats, which showed that rainfall favored seropositivity of T. gondii, whereas temperature, humidity and elevation did not [26]. Studies in Middle Java using a GIS system identi ed some important factors, low elevation, un ltered water sources, contact with raw meat and the high density of cats are supposed to be risk factors of toxoplasmosis in Middle Java [4].
Taken together, this study identi ed that T. gondii infection was common in livestock (sheep and goats, swines, cattle and yaks), pets (cats, dogs) and humans in China. As an important foodborne zoonotic parasite, T. gondii poses a great threat to human health and animals with various routes of infection. Hence, great attention should be paid to the prevention and control of T. gondii in livestock, pets and humans in China. Certain measures can be taken to prevent the prevalence of T. gondii infection in China. Some of these measures are strengthening the management of livestock farms, keeping the barn clean, preventing feline excreta from polluting environment, using ltered water or water boiling, wearing gloves when handling raw meat, and improving the practice of good hand hygiene.

Conclusion
Information on the prevalence of infection in livestock, pets and humans can be useful for assessing T. gondii environmental contamination and the risk for public health. The use of GIS geographic information system has become a key method to map the geospatial distribution of toxoplasmosis and evaluating the effectiveness of disease in the prevention. The present study, providing the geographical distribution map of epidemiology of T. gondii, indicated that infection with T. gondii was widespread in China, with a wide range of variation. However, there are also some limitations in this study. Some experiments data haven't published in the journal due to a variety of reasons, as such restricted the search for this part of the data. But it would hardly in uence the spatial distribution of toxoplasmosis from a macro view. Therefore, effective prevention and control strategies of toxoplasmosis are proposed to include strengthening the management of livestock farms, keeping the barn clean, preventing feline excreta from polluting environment, using ltered water or water boiling, wearing gloves when handling raw meat and improving the practice of good hand hygiene. TaiWan. Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.