Vector-borne diseases are human illnesses caused by parasites, viruses, and bacteria that are transmitted by vectors. In most cases, but not all, the vector is a female mosquito in search of a blood meal. Vector-borne diseases account for more than 17% of all infectious diseases and cause more than 700,000 deaths annually worldwide   (World Health Organization, 2020b) .

Mosquito borne Diseases

Malaria

Basic Information

Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes. It is preventable and able to be cured. In 2021, there were an estimated 247 million cases of malaria worldwide. The estimated number of malaria deaths stood at 627,000 in 2020. The WHO African Region carries a very high share of the global malaria burden. In 2021, the region was home to 95% of malaria cases and 96% of malaria deaths. Children under five accounted for about 80% of all malaria deaths in the region (World Health Organization, 2022e).

Symptoms

Some symptoms include fever, aching head, chills, and flu-like symptoms within 10–15 days. Left untreated, Plasmodium. falciparum malaria (P. falciparum) can progress to severe illness and death within a period of 24 hours. Treatment with an effective antimalarial drug can prevent a mild case from progressing to severe disease or death. (World Health Organization, 2022e)

Controls

Malaria can be prevented by effective vector control and the use of preventive antimalarial drugs. Vector controls consist of insecticide-treated nets, indoor residual spraying, outdoor spraying and other methods such as adding chemicals to water bodies and use of insect repellents. Preventative drugs or medicines are used either alone or in combination to prevent malaria infections and their consequences. Since October 2021, WHO also recommends broad use of the malaria vaccine among children living in regions with moderate to high P. falciparum malaria transmission. The vaccine has been shown to significantly reduce malaria, and deadly severe malaria, among young children (World Health Organization, 2022e). Over the past 15 years, Malaria occurrence in sub-Saharan Africa has been cut by 45%, primarily due to the massive use of insecticide-treated bed nets and spraying of residual insecticides inside houses (World Health Organization, 2017b).

Yellow Fever

Basic Information

Yellow fever is an epidemic-prone, mosquito-borne, vaccine-preventable disease that is transmitted to humans through the bites of infected Aedes aegpti and Haemagogus mosquitoes. These day-biting mosquitoes breed around houses, in forests or jungles, or in both habitats (World Health Organization, b).

Symptoms

Many people do not experience symptoms, but when these do occur, the most common are fever, muscle pain with prominent aching back and head, loss of appetite, and nausea or vomiting. In most cases, symptoms disappear after 3–4 days. A small percentage of patients enter a second, more harmful phase within 24 hours of recovering from initial symptoms. High fever returns and several body systems are affected, usually the liver and kidneys. In this phase people are likely to develop jaundice, dark urine and abdominal pain with vomiting. Bleeding can occur from the mouth, nose, eyes, or stomach. Half of these patients die within 7–10 days (World Health Organization, b).

Controls

Vaccination is the single most important measure for preventing yellow fever. The prevention of outbreaks can only be achieved if the majority of the population is immunized. The yellow fever vaccine is safe and affordable, and a single dose provides life-long immunity against the disease. Use insect repellent, wear long-sleeved shirts and pants, permethrin treated clothing, or use screens and nets (World Health Organization, b).

West Nile Virus

Basic Information

West Nile virus (WNV) can cause a deadly neurological disease in humans. However, approximately 80% of people who are infected will not show any symptoms. West Nile virus is mainly transmitted to people through the bites of infected Culex mosquitoes. Birds are the natural hosts of West Nile virus (World Health Organization, 2017c). West Nile virus is the leading cause of mosquito-borne disease in the continental United States (CDC, 2022d).

Symptoms

Most people (8 out of 10) infected with West Nile virus do not develop any symptoms. About 1 in 5 people who are infected develop a fever with other symptoms such as aching head, body aches, joint pains, vomiting, diarrhea, or rash. Most people with febrile illness due to West Nile virus recover completely, but tiredness and weakness can last for weeks or months. About 1 in 150 people who are infected develop a severe illness affecting the central nervous system such as encephalitis or meningitis (CDC, 2022e).

Controls

There is no vaccine to prevent WNV infection. The best way to prevent it is to protect yourself from mosquito bites. Use insect repellent, wear long-sleeved shirts and pants, treat clothing and gear, and take steps to control mosquitoes indoors and outdoors (CDC, 2020).

Dengue

Basic Information

Dengue is a viral infection transmitted to humans through the bite of infected mosquitoes. The primary vectors that transmit the disease are Aedes aegypti and Aedes albopictus mosquitoes. There are four dengue serotypes, and it is possible to be infected four times. Severe dengue is a leading cause of serious illness and death in some Asian and Latin American countries. It requires management by medical professionals. There is no specific treatment for dengue or severe dengue. Early detection of disease progression associated with severe dengue and access to proper medical care lowers death rates of severe dengue to below 1%. Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas. The global occurrence of dengue has grown a lot with about half of the world's population now at risk. Although an estimated 100–400 million infections occur each year, over 80% are generally mild and asymptomatic (World Health Organization, 2022c).

Symptoms

Dengue should be suspected when a high fever (40°C/104°F) is accompanied by two of the following symptoms during the febrile phase (2–7 days): severe aching head, pain behind the eyes, muscle and joint pains, nausea, vomiting, swollen glands, or rash. Severe dengue is a potentially deadly complication, due to plasma leaking, fluid accumulation, respiratory distress, severe bleeding, or organ impairment. Warning signs that doctors should look for include: severe abdominal pain, continual vomiting, rapid breathing, bleeding gums or nose, tiredness, restlessness, liver growth, blood in vomit or stool (World Health Organization, 2022c).

Controls

Dengue prevention and control depends on effective vector control measures such as prevention of mosquito breeding and using personal household protection measures, such as window screens, repellents, coils and vaporizers. Continuing community involvement such as educating the community on the risks of mosquito-borne diseases can greatly improve vector control efforts (World Health Organization, 2022c). A new dengue vaccine is approved for use in children ages 9–16, with laboratory-confirmed previous dengue virus infection, and living in areas where dengue is endemic (CDC, 2021).

Chikungunya

Basic Information

Chikungunya is a disease that circulates quickly and is transmitted to humans by infected Aedes aegypti and Aedes albopictus mosquitoes. The disease mostly occurs in Africa, Asia, and the Indian subcontinent. However, a major outbreak in 2015 affected several countries of the Region of the Americas, and occasional outbreaks are seen elsewhere. The disease shares some clinical signs with dengue and Zika and can be wrongly diagnosed in areas where they are common (World Health Organization, 2017a).

Symptoms

It is characterized by an abrupt beginning of fever, frequently accompanied by joint pain. The joint pain is often very weakening; it usually lasts for a few days, but may be prolonged for weeks, months or even years. Other common signs and symptoms include muscle pain, joint swelling, aching head, nausea, tiredness, and rash (World Health Organization, 2017a). Severe cases and deaths from chikungunya are very rare and are almost always related to other existing health problems (Pan American Health Organization, Chikungunya).

Controls

There is no commercial vaccine available to protect against chikungunya virus infection (World Health Organization, 2022b). Prevention and control rely heavily on reducing the number of natural and artificial water-filled container habitats that support breeding of the mosquitoes. For protection during outbreaks of chikungunya, clothing which minimizes skin exposure to the day-biting vectors is advised. Repellents can be applied to exposed skin or to clothing in strict agreement with product label instructions (Pan American Health Organization, 2013).

Zika

Basic Information

Zika virus disease is caused by a virus transmitted primarily by infected Aedes species mosquitoes (Ae. aegypti and Ae. albopictus). These are the same mosquitoes that spread dengue and chikungunya viruses. Aedes mosquitoes bite during the day. Although cases of Zika virus disease declined from 2017 onwards globally, transmission persists at low levels in several countries in the Americas and other endemic regions (World Health Organization, 2022h).

Symptoms

Symptoms are generally mild and include fever, rash, conjunctivitis, muscle and joint pain, malaise or aching head. Symptoms typically last for 2–7 days. Most people with Zika virus infection do not develop symptoms. Zika virus infection during pregnancy can cause infants to be born with microcephaly and other congenital deformities, known as congenital Zika syndrome. Infection with Zika virus is also associated with other complications of pregnancy including preterm birth and miscarriage. Zika virus infection is also a trigger of Guillain-Barré syndrome, neuropathy and myelitis, particularly in adults and older children (World Health Organization, 2022h).

Controls

Protection against mosquito bites during the day and early evening is a key measure to prevent Zika virus infection. Special attention should be given to prevention of mosquito bites among pregnant women, women of reproductive age, and young children. Personal protection measures include wearing clothing (preferably light-colored) that covers as much of the body as possible; using physical barriers such as window screens and closed doors and windows; and applying insect repellent to skin or clothing that contains DEET, IR3535 or icaridin. It is important to eliminate mosquito breeding sites, including covering water storage containers, removing standing water in flowerpots, and cleaning up garbage and used tires. No vaccine is yet available for the prevention or treatment of Zika virus infection (World Health Organization, 2022h).

Tick-borne diseases

Tick-borne Encephalitis

Basic Information

Tick-borne encephalitis (TBE) virus is spread through the bite of an infected Ixodidae tick. TBE virus can be found in parts of the region stretching from western and northern Europe through northern and eastern Asia. People who travel to these areas might be at risk for infection. TBE virus is not found in the United States. The ticks that spread TBE virus are most active in warmer months (April through November). People who spend time outdoors in or near forests are at highest risk of being bitten by a tick infected with TBE virus (CDC, 2022c).

Symptoms

Many people infected with tick-borne encephalitis (TBE) virus do not have symptoms. Initial symptoms can include fever, aching head, vomiting, and weakness. A few days later, severe symptoms can develop including being confused, loss of coordination, difficulty speaking, weakness of the arms or legs, and seizures. Severe disease often includes infection of the brain (encephalitis) or the membranes around the brain and spinal cord (meningitis) (CDC, 2022c).

Controls

The best way to prevent TBE is to protect yourself from tick bites. Use insect repellent and treat clothing and gear with 0.5% permethrin. Inspect your body and clothing for ticks during and after outdoor activities (CDC, 2022c).

Lyme Disease

Basic Information

Lyme disease is the most common vector-borne disease in the United States. Lyme disease is caused by the bacterium Borrelia burgdorferi which is spread to people through the bite of an infected blacklegged tick. Ticks can attach to any part of the human body but prefer hard-to-see areas such as the groin, armpits, and scalp. In most cases, the tick must be attached for 36–48 hours or more before Lyme disease bacteria can be transmitted (CDC, ).

Symptoms

Signs and symptoms of early Lyme disease include: a characteristic skin rash, called erythema migrans, tiredness, chills and fever, aching head, muscle and joint pain and swollen lymph nodes. Erythema migrans is a reddish or purple colored rash that usually appears 3–14 days after the bite of an infected tick. It typically appears at the site of the tick bite, is round or oval, and expands gradually over the course of several days. The center of the rash may clear as it enlarges, eventually resulting in a “bull’s-eye” appearance. If left untreated, infection can spread to joints, the heart, and the nervous system. Late Lyme disease can result in arthritis or swelling, usually in one or more large joints. Nervous system symptoms can include numbness, pain, nerve paralysis. Rarely, irregularities of the heart rhythm may occur (CDC, ).

Controls

Tick bite prevention can be done by using insect repellents containing DEET, picaridin, IR3535, oil of lemon or eucalyptus. Wear clothing treated with 0.5% permethrin. Re-treat clothing annually according to label instructions. It is recommended that you shower as soon as possible after spending time outdoors and that you check for ticks daily (CDC, ).

Rocky Mountain Spotted Fever

Basic Information

Is most often transmitted by the American dog tick in the Eastern, Central, and Western United States; by the Rocky Mountain wood tick in the Rocky Mountain states; and by the brown dog tick in the Southwestern United States along the U.S.-Mexico border. RMSF can be rapidly deadly if not treated within the first five days of symptoms (CDC, 2022a).

Symptoms

Early symptoms include high fever, severe aching head, malaise, myalgia edema around eyes and on the back of hands, gastrointestinal symptoms (nausea, vomiting, anorexia). A dotted red rash can appear on the skin giving it the name spotted fever. Advanced symptoms include altered mental status, coma, cerebral edema, respiratory compromise (pulmonary edema, ARDS), necrosis, requiring amputation, and multiorgan system damage (CNS, renal failure) (CDC, 2022a).

Controls

Tick Removal

Step One

Use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible. The key is to remove the tick as soon as possible. Avoid using nail polish, petroleum jelly, or heat to make the tick leave the skin (CDC, 2022b).

Step Two

Pull upward with steady, even pressure. Don’t twist or jerk the tick; this can cause the mouth-parts to break off and remain in the skin.  If you are unable to remove the mouth parts easily, leave them alone and let the skin heal (CDC, 2022b).

Step Three

After removing the tick, thoroughly clean the bite area and your hands with rubbing alcohol, an iodine scrub, or soap and water (CDC, 2022b).

Zoonotic Diseases

Zoonosis

Plague-fleas

Basic Information

Fleas can carry the plague. Plague is an infectious disease caused by the bacteria Yersinia pestis, a zoonotic bacterium, usually found in small mammals and their fleas. The disease is transmitted between animals via their fleas and can also transmit from animals to humans. Humans can be contaminated by the bite of infected fleas, through direct contact with infected fleas. Historically, plague was responsible for widespread pandemics with high mortality. It was known as the "Black Death" during the fourteenth century, causing more than 50 million deaths in Europe. Today it can be easily treated with antibiotics and the use of standard preventative measures. If left untreated it can have a case fatality rate between 30% and 100%.  Plague is found on all continents except Oceania, but most human cases since the 1990s have occurred in Africa. Democratic Republic of Congo, Madagascar, and Peru are the three most endemic countries (World Health Organization, 2022f).

Symptoms

There are three types of plague, and the symptoms depend on the type of plague.

Bubonic Plague:

Bubonic plague is the most common. The Yersinia pestis enters at the bite and travels to the nearest lymph node to make copies of itself. The lymph node becomes inflamed, tense and painful, and is called a bubo. At advanced stages of the infection the inflamed lymph nodes can turn into open sores filled with pus (World Health Organization, 2022f).

Septicemic Plague:

Septicemic plague occurs when infection spreads through the bloodstream (World Health Organization, 2022f).

Pneumonic Plague:

Pneumonic plague, or lung-based plague, is the deadliest form of plague. Incubation can be as short as 24 hours. Any person with pneumonic plague may transmit the disease via droplets to other humans. Untreated pneumonic plague, if not diagnosed and treated early, can be deadly. However, recovery rates are high if detected and treated in time (World Health Organization, 2022f).

Controls

What are some ways to control diseases from fleas?

Informing people when zoonotic plague is present in their environment and giving advice on how they can protect themselves. Take precautions against flea bites and not handle animal carcasses. Avoid direct contact with infected tissues such as buboes or close exposure to patients with pneumonic plague.

Leishmaniasis-Sand Flies

Basic Information

Leishmaniasis is caused by protozoan parasites which are transmitted by the bite of infected female phlebotomine sandflies. The disease affects some of the poorest people and is associated with malnutrition, population displacement, poor housing, a weak immune system and lack of financial resources. Leishmaniasis is also linked to environmental changes such as removing forests, building of dams, irrigation schemes and urbanization. An estimated 700,000 to 1 million new cases occur annually. Only a small fraction of those infected by parasites causing leishmaniasis will eventually develop the disease (World Health Organization, 2022d).

What are some characteristics of populations affected by Leishmaniasis?

The disease affects some of the poorest people and is associated with malnutrition, population displacement, poor housing, a weak immune system and lack of financial resources. Leishmaniasis is also linked to environmental changes such as removing forests, building of dams, irrigation schemes and urbanization.

Symptoms

There are three main forms of leishmaniasis: visceral, cutaneous and mucocutaneous.

Visceral Leishmaniasis (VL):

Visceral leishmaniasis (VL), also known as kala-azar is deadly if left untreated in over 95% of cases. It is characterized by irregular bouts of fever, weight loss, growth of the spleen and liver, and anemia (World Health Organization, 2022d).

Cutaneous Leishmaniasis (CL):

Cutaneous leishmaniasis (CL) is the most common form of leishmaniasis and causes skin lesions, mainly ulcers, on exposed parts of the body, leaving life-long scars and serious disability or stigma (World Health Organization, 2022d).

Mucocutaneous Leishmaniasis:

Mucocutaneous leishmaniasis leads to partial or destruction of mucous membranes of the nose, mouth, and throat (World Health Organization, 2022d).

Controls

Prevention and control of leishmaniasis requires a combination of intervention strategies. Vector control helps to reduce or interrupt transmission of disease by decreasing the number of sandflies. Control methods include insecticide spray, use of insecticide-treated nets, environmental management and personal protection (World Health Organization, 2022d).

Brucellosis

Basic Information

Brucellosis is a bacterial disease caused by various Brucella species, which mainly infect cattle, swine, goats, sheep, and dogs. Humans generally acquire the disease through direct contact with infected animals, by eating or drinking contaminated animal products, or by inhaling airborne agents. Most cases are caused by drinking unpasteurized milk or cheese from infected goats or sheep. Human-to-human transmission is very rare. Brucellosis is one of the most widespread zoonoses transmitted by animals and in endemic areas. Brucellosis is found globally and is a reportable disease in most countries (World Health Organization, 2020a).

How do humans generally acquire brucellosis?

Through direct contact with infected animals, by eating or drinking contaminated animal products or by inhaling airborne agents. Most cases are caused by drinking unpasteurized milk or cheese from infected goats or sheep.

Symptoms

The disease causes flu-like symptoms, including fever, weakness, malaise, and weight loss. The incubation period of the disease can be highly variable, ranging from 1 week to 2 months, but usually 2–4 weeks (World Health Organization, 2020a).

Controls

Prevention of brucellosis is based on surveillance and the prevention of risk factors. The most effective prevention strategy is the elimination of infection in animals. Vaccination of cattle, goats, and sheep is recommended in enzootic areas with high prevalence rates. In countries where eradication in animals through vaccination or elimination of infected animals is not feasible, prevention of human infection is primarily based on raising awareness, food-safety measures, occupational hygiene, and laboratory safety. Pasteurization of milk for direct consumption and for creating cheese is an important step to preventing transmission from animals to humans. Education campaigns about avoiding unpasteurized milk products can be effective, as well as policies on its sale (World Health Organization, 2020a).

Chagas Disease- Trypanosoma Cruzi

Basic Information

Chagas disease, also known as American trypanosomiasis, is a potentially life-threatening illness caused by the protozoan parasite Trypanosoma cruzi (T. cruzi). About six million to seven million people worldwide are estimated to be infected with Trypansosoma cruzi, the parasite that causes Chagas disease. Chagas disease is found mainly in endemic areas of 21 continental Latin American countries, where it has been mostly transmitted to humans by contact with feces or urine of triatomine bugs (vector-borne), known as 'kissing bugs,' among many other popular names, depending on the geographical area. The infection has been increasingly detected in the United States of America, Canada, and many European and some African, Eastern Mediterranean, and Western Pacific countries. T. cruzi parasites are mainly transmitted by contact with feces or urine of infected blood-sucking triatomine bugs. These bugs typically live in the wall or roof cracks of homes and peri domiciliary structures, such as: chicken coops, pens, and warehouses, in rural or suburban areas. Normally they hide during the day and become active at night when they feed on animal blood, including human blood. They usually bite an exposed area of skin such as the face (hence its common name, kissing bug), and the bug defecates or urinates close to the bite. The parasites enter the body when the person instinctively smears the bug’s feces or urine into the bite, other skin breaks, or the eyes or the mouth (World Health Organization, 2022a).

Symptoms

Chagas disease presents in two phases. The initial acute phase lasts for about two months after infection. During the acute phase, a high number of parasites circulate in the blood, but in most cases the symptoms are absent or mild and unspecific. In less than 50% of people bitten by a triatomine bug, characteristic first visible signs can be a skin lesion or a purplish swelling of the lids of one eye. Additionally, they can present fever, aching head, enlarged lymph glands, pallor, muscle pain, difficulty in breathing, swelling, and abdominal or chest pain. During the chronic phase, the parasites are hidden mainly in the heart and digestive muscle. One to three decades later, up to 30% of patients suffer from cardiac disorders and up to 10% suffer from digestive (typically growth of the esophagus or colon), neurological, or mixed alterations. In later years the infection in those patients can cause the destruction of the heart muscle and nervous system, consequent cardiac arrhythmias or progressive heart failure, and sudden death. Trypanosoma cruzi infection is able to be cured if treatment is initiated soon after infection (World Health Organization, 2022a).

Controls

There is no vaccine to prevent Chagas disease. Vector control has been the most effective method of prevention in Latin America. Prevention methods include spraying of dwellings and surrounding areas with residual insecticides, house improvements and house cleanliness to prevent vector infestation, personal preventive measures such as bed nets, good hygiene practices in food preparation, transportation, storage, and consumption, development and training of education materials for the community (World Health Organization, 2022a).

What are some prevention methods to control Chagas disease?

Spraying of dwellings and surrounding areas with residual insecticides, house improvements and house cleanliness to prevent vector infestation, personal preventive measures like bednets, good hygiene practices in food preparation, transportation, storage, and consumption, development and training of education materials for the community.

Ebola

Basic Information

Ebola virus disease (EVD), formerly known as Ebola hemorrhagic fever, is a rare but severe and often deadly fatal illness in humans. The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission. The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks. It is thought that fruit bats of the Pteropodidae family are natural Ebola virus hosts. Ebola is introduced into the human population through close contact with the blood, secretions, organs, or other bodily fluids of infected animals such as fruit bats, chimpanzees, gorillas, monkeys, forest antelope, or porcupines found ill or dead or in the rainforest. Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This occurs through close contact with patients when infection control precautions are not strictly practiced. Ebola then spreads through human-to-human transmission via direct contact with blood or body fluids of a person who is sick with or has died from Ebola or objects that have been contaminated with body fluids (like blood, feces, vomit) from a person sick with Ebola. Burial ceremonies that involve direct contact with the body of the deceased can also contribute to the transmission of Ebola (World Health Organization, 2021a).

Symptoms

The Ebola virus causes an acute, serious illness which is often deadly if untreated. People remain infectious as long as their blood contains the virus. The incubation period is from 2–21 days. A person infected with Ebola cannot spread the disease until they develop symptoms. Symptoms of EVD can be sudden and include fever, tiredness, muscle pain, aching head, and sore throat. These symptoms are followed by vomiting, diarrhea, rash, impaired kidney and liver function, internal and external bleeding (for example, oozing from the gums, or blood in the stools) (World Health Organization, 2021a). 

Controls

Community engagement is key to successfully controlling outbreaks. Good outbreak control relies on applying a package of interventions; namely case management, infection prevention and control practices, surveillance and contact tracing, a good laboratory service, safe and dignified burials, and working together to make a difference. Vaccines to protect against Ebola have been developed and have been used to help control the spread of Ebola outbreaks in Guinea and in the Democratic Republic of the Congo (DRC) (World Health Organization, 2021a).

What does good outbreak control of Ebola look like?

Applying a package for interventions: case management, infection prevention and control practices, surveillance and contact tracing a good laboratory service, safe and dignified burials, and social mobilization.

Rabies-Dogs

Basic Information

Rabies is a vaccine-preventable zoonotic viral disease (World Health Organization, 2021b). Rabies is estimated to cause 59 000 human deaths annually in over 150 countries, with 95% of cases occurring in Africa and Asia (World Health Organization, a). People are usually infected following a deep bite or scratch from an animal with rabies. Dogs are the main source of human rabies deaths, contributing up to 99% of all rabies cases in humans. However, human deaths have followed exposure to foxes, raccoons, skunks, jackals, and mongooses (World Health Organization, 2021b).

Symptoms

Early symptoms of a rabies infection can include a fever with pain and unusual or unexplained tingling, piercing or burning sensation at the wound site. In later states, the virus spreads to the central nervous system, causing deadly inflammation of the brain and spinal cord. The incubation period of the disease can vary from one week to one year, though it is typically 2–3 months (World Health Organization, a). Once clinical symptoms appear, rabies is virtually 100% deadly (World Health Organization, 2021b).

There are two forms of the disease. The two types of rabies show different symptoms. Furious rabies causes signs of hyperactivity, excitable behaviour, hydrophobia (fear of water) and sometimes aerophobia (fear of drafts or of fresh air). Death occurs after a few days due to cardio-respiratory arrest. Paralytic rabies, which accounts for about 20% of the total number of human cases, runs a less dramatic and usually longer course than the furious form. Muscles gradually become paralyzed, starting at the site of the bite or scratch. A coma slowly develops and eventually death occurs (World Health Organization, a).

Controls

Successful rabies control programs are comprised of three pillars: Eliminating rabies in dogs, Awareness on rabies and preventing dog bites, and Immunization of people. Vaccinating dogs is the most cost-effective strategy for preventing rabies in people. Education on dog behavior and bite prevention for both children and adults is an essential extension of a rabies vaccination program and can decrease the occurrence of human rabies. If a person is bit by a dog with rabies, they should immediately and thoroughly flush and wash the wound for a minimum of 15 minutes with soap and water, detergent, or other substances that remove and kill the rabies virus. This should be followed by an effective rabies vaccine. The same vaccine that is used to immunize people after an exposure can also be used before exposure to rabies (World Health Organization, 2021b).

What are the main parts of a rabies control program?

Mass vaccination of dogs, community participation; education, public awareness and access to mass vaccination of dogs; and access to post-bite treatment.

Snails-Schistosomiasis

Basic Information

Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes (trematode worms). Estimates show that at least 236.6 million people required preventive treatment in 2019 and has been reported from 78 countries. It is estimated that at least 90% of those requiring treatment for schistosomiasis live in Africa. People become infected when larval forms of the parasite are released by freshwater snails and penetrate the skin during contact with infested water. People are infected during routine agricultural, domestic, occupational, and recreational activities which expose them to the infested water. Lack of hygiene and certain play habits of school-aged children such as swimming or fishing in infested water make them especially vulnerable to infection. In the body, the larvae develop into adult schistosomes. Adult worms live in the blood vessels where the females release eggs. Some of the eggs are passed out of the body in the feces or urine to continue the parasite’s life cycle. Others become trapped in body tissues, causing immune reactions and progressive damage to organs (World Health Organization, 2022g).

Symptoms

In children, schistosomiasis causes anemia, stunted growth, and reduced ability to learn, although its effects are usually reversible with treatment. Chronic schistosomiasis can affect people’s ability to work and, in some cases, result in death.

Intestinal schistosomiasis can result in abdominal pain, diarrhea, and blood in the stool. Liver growth enlargement is common in advanced cases and is frequently associated with an accumulation of fluid in the peritoneal cavity and hypertension of the abdominal blood vessels. In such cases there may also be growth of the spleen.

Urogenital schistosomiasis is shown by the classic symptom of hematuria (blood in urine). Fibrosis of the bladder and ureter, and kidney damage are sometimes diagnosed in advanced cases. Bladder cancer is another possible complication in the later stages (World Health Organization, 2022g).

Controls

The control of schistosomiasis is based on large-scale treatment of at-risk population groups, access to safe water, improved sanitation, hygiene education, and snail control. Groups targeted for treatment include pre-school-aged children, school-aged children in endemic areas, adults considered to be at risk in endemic areas, and people with occupations involving contact with infested water, such as fishermen, farmers, irrigation workers, and women whose domestic tasks bring them in contact with infested water and entire communities living in highly endemic areas. Praziquantel is the recommended treatment against all forms of schistosomiasis. It is effective, safe, and low-cost. Even though re-infection may occur after treatment, the risk of developing severe disease is diminished and even reversed when treatment is initiated and repeated in childhood (World Health Organization, 2022g).

What should control of schistosomiasis be based on?

Large-scale treatment with praziquantel of at-risk population groups, access to safe water, improved sanitation, hygiene education, and snail control.

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