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Onchocerciasis is a parasitic disease caused by the filarial nematode worm Onchocerca volvulus. It is transmitted to humans by black flies (genus Simulium) The disease is commonly known as "river blindness" because the larvae of the blackfly vectors breed in fast-flowing rivers.

Symptoms

It can cause severe skin and eye disease, including blindness.

Actual situation and treatment

Onchocerciasis is endemic in Africa, and in 13 foci in six countries of the Americas (Brazil, Colombia, Mexico, Guatemala, Ecuador, and Venezuela), where it was introduced through the slave trade. The transmission has been interrupted or eliminated in 11 of 13 foci of the Americas. As a result of a regional initiative, only about 20,495 people are still in need of continual treatment in Brazil and Venezuela (Yanomami indigenous population). Furthermore, Colombia is the first country in the world to achieve the verification of Onchocerciasis elimination.

Plague is a zoonotic disease that circulates mainly between rodents and other small animals, in areas of natural foci in various parts of the world. In the Americas, there are foci in 5 countries (Bolivia, Brazil, Ecuador, the United States, and Peru). 
The etiological agent, the bacteria Yersinia pestis can also infect humans and this disease can be very severe and of epidemic potential. 

Transmission

The most frequent transmission between animals and humans is through the bites of infected fleas. Other forms of transmission can be through direct or indirect contact with animals. It can also be transmitted by inhalation of aerosolized droplets from one infected person to another. 

Symptoms

There are different clinical manifestations of plague in humans, pneumonia is the most serious with high lethality and mandatory notification under the International Health Regulations. 

Treatment

Plague can be treated with antibiotics, and it is very important to recognize the disease early.

Schistosomiasis is a chronic parasitic infection caused by worms. It is most common in rural and impoverished populations. In the Americas, the parasite species is Schistosoma mansoni, which is associated with intestinal schistosomiasis.

Transmission
The main risk factor for infection is exposure through the household, work, or recreational activities in freshwater contaminated with feces from infected humans. In the Region, for transmission to occur, Biomphalaria snails, the intermediate hosts of the parasite, must also be present in contaminated water. Children and adolescents are the populations most at risk.

Symptoms
Chronic infection can result in anemia, liver and intestinal fibrosis, spleen enlargement, and in serious cases, neurologic complications and death. Schistosomiasis claims the lives of children and adults in the Americas each year.

West Nile virus is a member of the flavivirus genus and belongs to the Japanese encephalitis antigenic complex of the family Flaviviridae. It is transmitted by infected mosquitoes between and among humans and animals, including birds, which are the virus's reservoir host.

First isolated in the West Nile district of Uganda in 1937, WNV is today found commonly in Africa, Europe, the Middle East, North America, and West Asia. In 1999 a WNV circulating in Israel and Tunisia was imported into New York producing a large outbreak that spread across the United States and eventually across the Americas, from Canada to Venezuela. WNV outbreak sites are found along major bird migratory routes.

Yellow fever is an acute viral hemorrhagic disease that is endemic in tropical areas of Africa and Latin America. Cases can be difficult to distinguish from other viral hemorrhagic fevers such as arenavirus, hantavirus or dengue.

Symptoms
Usually appear 3 to 6 days after the bite of an infected mosquito. In the initial phase, they include fever, muscle pain, headache, shivers, loss of appetite, and nausea or vomiting. For most patients, these symptoms disappear after 3 to 4 days. However, 15% of patients enter a second, more toxic phase within 24 hours of the initial remission when high fever returns, and several body systems are affected, including the kidneys. 

Treatment
Treatment is symptomatic, aimed at reducing symptoms for the comfort of the patient; vaccination is the most important preventive measure against yellow fever, is safe, affordable and highly effective, providing effective immunity within 30 days for 99% of those vaccinated. A single dose is sufficient to confer sustained immunity and life-long protection, with no need for a booster.

Zika is a disease contracted through the bite of an infected mosquito. When a mosquito feeds on the blood of an infected person and then bites others, it passes Zika to them. There is documentation that the infection can also be passed from mother to child, sexually, and through blood transfusions.

Aedes aegypti is the mosquito that carries Zika, as well as dengue, chikungunya and yellow fever. This mosquito lives in and around dwellings and reproduces in any receptacle that contains water.

There are reports of an association between Zika virus infection, Guillain-Barré syndrome and microcephaly.

• Training videos for vector control workers