Silent Killer: Beware of zoonotic diseases around you

Zoonotic disease refers to a class of diseases caused by common pathogens in humans and vertebrates and are epidemiologically related. At present, there are more than 200 species of zoonotic diseases that can be naturally transmitted between humans and animals in the world, and there are about 130 species in China.

With the change of ecological environment and the deepening of international exchanges, some diseases have crossed their own epidemic scope to achieve cross-border, cross-continent and cross-oceanic transmission, some major epidemics that have been basically controlled in the past have relapsed, the pathogens that existed only in animals in the past have been transmitted to humans, and some pathogens that have not been pathogenic or lowly pathogenic to humans in the past have gradually become pathogenic pathogens that are strongly pathogenic to humans, and even the emergence of some emerging diseases is also accelerating. In recent years, some major zoonotic diseases such as COVID-19, SARS, MERS, Zika virus disease, rabies, brucellosis, malaria, tuberculosis, kala-azar, echinococcosis and other major zoonotic diseases have not only posed a huge threat to human and animal health, but also caused great trauma to the global economy, led to huge economic losses, and caused unprecedented international panic. Xiaobian has collected and sorted out some of the knowledge of prevention and control of zoonotic diseases that are highly prevalent and easily overlooked around us to improve our understanding of these zoonotic diseases.

Babesiosis

Babesiasis is a worldwide zoonotic disease caused by infection with Babesia by humans or mammals such as cattle, horses, and dogs. Babes are mainly parasitic in human or other vertebrate red blood cells and are transmitted by tick vectors or blood transfusions. In 1888, when the Hungarian scientist Babes investigated the symptoms of fever and hematuria in some local cattle and the causes of death, Babes was first detected in cattle. In 1893, two other scholars confirmed that B. Bergeronii (B. 2007). Bigemina) can infect Texas cattle through tick-borne transmission, and the study is the first to experimentally confirm that Babes can be transmitted by medical arthropod vector ticks. The earliest infestation of Babesia in China can be traced back to the series of reports by Professor Hong Shilu on the cases of "animal malaria parasite" infection in Chongqing in 1943. In 1957, the first human babesia case was found by Yugoslav scholars in a splenectomy patient, and finally identified as divergent babes infection, which is also considered to be the earliest reported case of human babesia infection in the world; and the above-mentioned human babesia case report described by Professor Hong Shilu in China was more than 10 years earlier than the case.

Babesiosis is a new parasitic disease that is endemic worldwide in Europe, Asia, Africa, North and South America and Australia, with the United States having the highest number of cases of babesiosis. Babesiosis in China is mainly distributed in the northeast region, followed by the southwest region.

Babesiasis is globally distributed and the population is generally susceptible, occurring more often in summer and autumn. Although babesia infection is often considered non-lethal in immunocompetent people, for immunocompromised people, babesia infection patients have different degrees of autoimmune hemolysis, which is more harmful and should be paid more attention to.

II. Toxoplasmosis (toxoplasmosis)

Toxoplasmosis is a zoonotic parasitic disease caused by infection with the parasitic protozoa toxoplasma gondii in the opportunistic cells of the apical compound gate. Toxoplasma gondii has been around for 110 years since it was first discovered, and its infection is distributed worldwide. It is estimated that about one-third of the global population is positive for toxoplasma gondii serum antibodies, but there are significant geographical differences in infection rates. The positive rate of toxoplasmosis antibodies in European and American populations is 25% to 50%, and in the 1960s, surveys found that the positive rate of toxoplasmosis antibodies in a few developed countries exceeded 80%.

In recent years, due to the pretreatment of meat products before marketing, the infection rate of Toxoplasma gondii in Europe has shown a significant downward trend, but it is still around 40%. China has conducted two large-scale seroepidemiological surveys throughout the country. In 1983–1986, the Indirect Hemagglutination Test (IHA) was used to survey 81,968 residents in 141 counties in 19 provinces (municipalities directly under the Central Government, Autonomous Regions), and the average positive rate of anti-Toxoplasmosis antibodies was 5.16 per cent; in 2001–2004, 47,444 people were tested in 15 provinces (municipalities directly under the Central Government, Autonomous Regions) using enzyme-linked immunosorbent assay (ELISA) and an average positive rate of anti-Toxoplasma antibodies was 7.88%.

Toxoplasmosis is a foodborne opportunistic parasitic disease that is generally susceptible to Toxoplasma gondii and has a high risk of infection (manifested as positive seroant antibodies) mainly associated with unclean and poor eating habits and pet keeping. Infections in meat livestock and poultry cause economic losses in the farming industry and are also a potential risk of human infection. It is known that the pathological changes caused by Toxoplasma gondii infection are mainly histimatitis and necrosis caused by the proliferation of insects, followed by apoptosis induced by certain effector molecules. In general, the strength of toxoplasma gondii pathogenicity depends on the strain's virulence, proliferation rate, and host species. Toxoplasma gondii infection in immunocompetent patients is usually self-limiting or has no obvious clinical manifestations, but a small number of people will have clinical symptoms such as toxoplasmosis encephalopathy or eye disease after infection; infection with toxoplasmosis in immunocompromised patients may trigger potential infection reactivation, leading to fatal clinical outcomes. After acute infection of toxoplasma gondii in pregnant women during pregnancy (especially in the first trimester), the proliferation of the worm can destroy the placental barrier and directly invade the fetus, resulting in serious adverse pregnancy outcomes such as miscarriage, premature birth, and stillbirth.

Trichinellosis

Trichinellosis is a foodborne zoonotic parasitic disease caused by trichinella infection. The disease is worldwide, and people infected by raw or semi-raw meat containing live larvae sacs can cause symptoms such as fever, rash, muscle pain, and facial or eyelid edema, and severe patients can die from complications such as pneumonia, encephalitis, or myocarditis. The worm was first discovered in human muscles in 1828 and has a history of nearly 200 years, but its harm to animals, humans and society has never diminished.

Trichinellosis is distributed worldwide, and animal or human infection with trichinella has been reported in 66 countries and regions around the world. Presumably, at least 11 million people worldwide are currently suffering from trichinellosis, which is considered one of the resurgence of diseases. Trichinella has been severely endemic in Europe and North America, and in recent years the rate of trichinella infection has shown a significant downward trend due to strict quarantine before meat and meat products are marketed. At present, trichinellosis is still seriously endemic in Russia and Eastern European countries (Belarus, Bulgaria, Ukraine, Croatia, etc.), Argentina, Mexico and Vietnam, Thailand, Laos and other places. The epidemic of trichinellosis in China is relatively serious, due to the lack of diet, cooking, hygiene habits and meat quarantine in some areas and ethnic groups, trichinellosis outbreaks occur from time to time, and have endemic, group and food-borne characteristics. From 1964 to 2011, more than 600 outbreaks of trichinellosis occurred in 15 provinces (municipalities directly under the central government and autonomous regions) including Yunnan, Sichuan, Henan, Guangxi and Beijing, with a cumulative number of 38 797 cases and 336 deaths. Since 2000, a total of 21 outbreaks of human trichinellosis have been reported in 7 prefectures (cities) in Yunnan Province, with a total of 2,256 cases and 3 deaths; the patients are the oldest 90 years old, the youngest is only 9 months, mostly young adults, all related to the habit of local ethnic minorities to eat raw meat. In addition, in 2006, an outbreak of trichinellosis imported from abroad (Laos) in Pu'er City for the first time in China had 49 cases. The second national survey report on the status of important parasitic diseases in the human body shows that the seroprevalence rate of trichinella in the population of 10 provinces (municipalities directly under the central government and autonomous regions) is 3.31%, the highest in Yunnan Province (8.26%), followed by Inner Mongolia (6.25%) and the lowest in Liaoning Province (0.26%).

Trichinellosis is a foodborne zoonotic parasitic disease. According to the survey, more than 150 species of mammals, including carnivores, omnivores, rodents, herbivores and carnivores, and even some birds and birds are susceptible to trichinella, which maintain their life history by eating carrion or killing each other, resulting in the circulation and transmission of the disease in the biological chain of wild and domestic animals. Trichinellosis is listed as a second-class animal disease by the Ministry of Agriculture and Rural Affairs of China, which is a mandatory inspection and quarantine project for meat products in China, and livestock infection not only causes economic losses in the breeding industry, but also is a potential risk of human infection. In addition to Hainan Province, all provinces (municipalities directly under the Central Government, autonomous regions) in China have relevant reports of animal trichinella infection, especially in the southwest, central plains and northeast regions of the pig trichinella infection rate is high, and because Chinese residents eat more pork, so pigs and human infection are the closest relationship, pork and related products are still the main source of human infection in China. At present, although pork is still the main meat that causes outbreaks of trichinellosis, the source of infection in outbreaks is shifting from pork to dog meat, herbivores and even wild animal meat.

Cryptosporidiosis

Cryptosporidium is an emerging infectious disease caused by zoonotic intestinal protozoa cryptosporidium infection, one of the six major diarrheal diseases in the world. The disease is mainly transmitted by water. In 2006, the WHO classified cryptosporidiosis as a neglected disease. In 1997, Cryptosporidium was listed as a foodborne parasite by the US CDC, which is considered to be the second largest pathogen causing diarrhea or death in children after rotavirus, and is also one of the top ten pathogens monitored by the US foodborne disease active surveillance system FoodNet. Cryptosporidium disease is mainly infected by ingestion of food and water contaminated with cryptosporidium oocysts, causing watery diarrhea, abdominal pain, nausea, vomiting and other symptoms; in immunocompetent patients usually present as asymptomatic or self-limited diarrhea of about two weeks, while immunocompromised patients present with cholera-like diarrhea and even life-threatening diarrhea.

Cryptosporidiosis is globally distributed, with 0.6% to 13% of cryptosporidium infection rates in developed countries and 4% to 20% in developing countries. The infection rate of Cryptosporidium in different provinces of China is 0.65% to 11.15%: children (2.56%), diarrhea patients (2.75%), adolescents (3.68%), hepatitis B patients (4.89%), HIV infected people (6.57%), drug addicts (24.14%) and cancer patients (47.79%) Cryptosporidium infection rate is higher than that of adults (1.89%); the infection rate of rural population (1.77% to 12.87%) is significantly higher than that of urban (0% ) ~3.70%); the infection rate of Cryptosporidium varied significantly in different seasons, with the peak of infection in summer and autumn. Cryptosporidium is not only one of the causes of persistent diarrhea in immunodeficient patients, but also a common cause of traveler's diarrhea. There have been reports of higher positive rates of Cryptosporidium among patients with diarrhea travelling to South Asia. Travel from developed countries to developing countries is one of the risk factors for cryptosporidiosis. From 2001 to 2003, the infection rate of Cryptosporidium was 1.3% among patients with traveler's diarrhea who traveled from developed countries and regions to Nepal. From 2003 to 2010, 3.0% of patients with traveler's diarrhea traveled to Peru from developed countries such as North America and Europe were infected with Cryptosporidium. In 2005-2007, the infection rate of Cryptosporidium was 6.4% among travelers with diarrhea returning from a trip to Mexico in the United States.

V. Giardiasis

Giardiasis, also known as Giardiasis, is a type of intestinal protozoa caused by giardiasis infection, which first occurred in 1976 in a group infection among tourists, so it is also called "traveler's diarrhea", which is prone to growth and development disorders and cognitive impairment in children infected. In 1681, the Dutch scholar van Leeuwenhoek first discovered the giardia trophozoite in his diarrhea feces, lambel named it intestinal giardia in 1859, and Stiles officially named it Giardia blue in 1915. Giardia is currently the only species of Giardia that can infect humans and is distributed globally, mostly in temperate and tropical regions. In 2010, there were an estimated 179 million infected people worldwide, with an average of 280 million new infections per year, and children under 10 years of age in developing countries are high-risk groups, with an average infection rate of 15% to 20%. Developed countries, such as the United States, Canada and Australia, not only have the epidemic of this insect, but also have a tendency to increase year by year. Because the disease has been endemic among international travelers, it is the most commonly isolated parasitic pathogen among travelers.

People are mainly infected by ingesting water and food contaminated by the faecal-oral route, clinical manifestations are diarrhea, abdominal cramps, bloating, weight loss and malabsorption disorders, diarrhea in immunocompetent patients can be self-limited, while immunosuppressed people can cause persistent diarrhea, severe cases can lead to death, asymptomatic giardiasis is also more common. In addition to humans, mammals such as cattle, sheep, pigs, cats and dogs are also infected with the worm. Giardia capsules can survive in water for months, and travelers can become infected on the journey by contact with drinking water, recreational water, or food contaminated with giardia sacs, and the risk of infection increases with the length of travel. Giardiasis is common in areas with poor economic or sanitary conditions and is strongly associated with low income and lack of sanitation infrastructure. In developed countries, about 2 per cent of adults and 8 per cent of children have been infected with GIARDIA and in developing countries, while in developing countries there is a history of previous GIARDIS infections approaching 33 per cent. Giardiasis is listed as one of the 10 major parasitic diseases that endanger human health globally, and in 2004 the WHO classified it as a neglected disease.

The incubation period for giardia infestation averages 1 to 2 weeks, with the longest reaching 45 days. In the acute phase, diarrhea stool is watery, foul-smelling, generally bloodless, mucus and cellular exudate, often accompanied by fever, significant bloating and abdominal pain. In such patients, giardia infection should be considered if antimicrobial therapy is ineffective. In general, patients in the acute phase can be transferred to subacute or chronic phases if they are not treated in a timely manner. Most patients present with persistent or recurrent moderate to mild symptoms. Subacute patients present with intermittent foul-smelling soft stools or thin porridge-like stools with gastrointestinal symptoms such as flatulence, bloating, or cramping pain in the abdomen, nausea, vomiting, and anorexia. Once chronic, symptoms recur, and patients present with periodic loose stools, foul odor, no mucus, and pus and blood, and the course of the disease can reach several years. A significant proportion of infected people (13% of adults and about 17% of children) do not show any clinical symptoms and become asymptomatic carriers. Most of these patients have varying degrees of intestinal pathological changes and malabsorption dysfunction. For children with acute and chronic diarrhea, the possibility of giardia infection should be considered in those who do not respond to antibiotic symptomatic therapy.

To be continued...

Zoonoses is the world's first gold-source journal to quickly report on zoonotic communicable diseases. The journal aims to bridge communication between researchers, clinicians, veterinarians and public health scholars in the field of zoonoses, and to provide a rapid and open platform for the latest discoveries, methods and perspectives in the fields of clinical medicine, veterinary medicine and public health. The journal will publish the latest research on the epidemiology, etiology, biology, diagnosis, prevention, treatment and management of viral, bacterial, parasitic, fungal zoonotic diseases. Zoonoses is co-editor-in-chief by Professor Dong Xiaoping, Chief Scientist of Virology at the Chinese Center for Disease Control and Prevention, and Professor Lynn Soong of the University of Texas Medical Division.