Dengue and chikungunya

 

Dengue and chikungunya

What is Dengue?

Dengue pronounced den ‘gee is a viral disease.Dengue can be caused by infection with any one of four closely related Dengue viruses.

DENV 1, DENV 2, DENV 3, DENV 4.

How does it spread?

The dengue viruses are transmitted to humans by the bite of an infected AEDES.

Characteristics of the AEDES mosquito?

One distinct physical feature ( black and white stripes on its body and legs), Hence also called as tiger Mosquito. bites during the day, Lays its eggs in clean, stagnant water.

Did you know?

Only the female AEDES mosquito as it needs the protein in blood to develop it eggs. the mosquito becomes infective approximately seven days after it has bitten a person carrying the virus. Once infected, A mosquito remains infective for life and passes on the virus to the eggs it lays. Peek biting time is at dawn and dusk – 2 hour after sunrise and 2 hour before sunset.

AEDES mosquito: fast facts

The average life span of an aedes mosquito is two weeks. the mosquito can lay eggs about three times in its life time, and about 100 eggs are produced each time.

The eggs can withstand very dry conditions (desiccation) and remain viable for many months in the absence of water. and repopulation will occur as soon as the eggs in the container are flooded with water.

Adults mosquito “usually” rests indoor in dark areas (closets under beds and behind curtains)

They have limited fight range – can fly an average of 400 mts. looking for water- filled container to lay their eggs. This means that people, rather than mosquitoes, rapidly move the virus within and between communities and places. 

A few mosquitoes per house hold can produce large dengue outbreaks. the dengue mosquito does not lay eggs in ditches, drainages, canals, wetlands, rivers and lakes.

The mosquito life cycle from egg to larva, pupae and to an adult mosquito, takes 8 days and occur in water. Humans develops disease after 5-6 days of being bitten by an infective mosquito.

What can you do reduce risk of acquiring dengue?

Protect yourself from mosquito bites.

Key facts

Vector-borne diseases account for more than 17% of all infectious diseases, causing more than 1 million deaths annually. More than 2.5 billion people in over 100 countries are at risk of contracting dengue alone. Malaria causes more than 400 000 deaths every year globally, most of them children under 5 years of age. Other diseases such as Chagas disease, leishmaniasis and schistosomiasis affect hundreds of millions of people worldwide. Many of these diseases are preventable through informed protective measures.

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Main vectors and diseases they transmit

Vectors are living organisms that can transmit infectious diseases between humans or from animals to humans. Many of these vectors are bloodsucking insects, which ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later inject it into a new host during their subsequent blood meal.

Mosquitoes are the best-known disease vector. Others include ticks, flies, sandflies, fleas, triatomine bugs and some freshwater aquatic snails.

Mosquitoes

Aedes

• Chikungunya
• Dengue fever
• Rift Valley fever
• Yellow fever
• Zika

Anopheles

• Malaria

Culex

• Japanese encephalitis
• Lymphatic filariasis
• West Nile fever

Sandflies

• Leishmaniasis
• Sandfly fever (phelebotomus fever)

Ticks

• Crimean-Congo haemorrhagic fever
• Lyme disease
• Relapsing fever (borreliosis)
• Rickettsial diseases (spotted fever and Q fever)
• Tick-borne encephalitis
• Tularaemia

Triatomine bugs

• Chagas disease (American trypanosomiasis)

Tsetse flies

• Sleeping sickness (African trypanosomiasis)

Fleas

• Plague (transmitted by fleas from rats to humans)
• Rickettsiosis

Black flies

• Onchocerciasis (river blindness)
• Aquatic snails
• Schistosomiasis (bilharziasis)

Vector-borne diseases

Vector-borne diseases are illnesses caused by pathogens and parasites in human populations. Every year there are more than 1 billion cases and over 1 million deaths from vector-borne diseases such as malaria, dengue, schistosomiasis, human African trypanosomiasis, leishmaniasis, Chagas disease, yellow fever, Japanese encephalitis and onchocerciasis, globally.

Vector-borne diseases account for over 17% of all infectious diseases.

Distribution of these diseases is determined by a complex dynamic of environmental and social factors.

Globalization of travel and trade, unplanned urbanization and environmental challenges such as climate change are having a significant impact on disease transmission in recent years. Some diseases, such as dengue, chikungunya and West Nile virus, are emerging in countries where they were previously unknown.

Changes in agricultural practices due to variation in temperature and rainfall can affect the transmission of vector-borne diseases. Climate information can be used to monitor and predict distribution and longer-term trends in malaria and other climate-sensitive diseases.

History:-

Although the parasite responsible for P. falciparummalaria has been in existence for 50,000–100,000 years, the population size of the parasite did not increase until about 10,000 years ago, concurrently with advances in agriculture and the development of human settlements. Close relatives of the human malaria parasites remain common in chimpanzees. Some evidence suggests that the P. falciparum malaria may have originated in gorillas.

References to the unique periodic fevers of malaria are found throughout recorded history. Hippocrates described periodic fevers, labelling them tertian, quartan, subtertian and quotidian. The Roman Columella associated the disease with insects from swamp.

Malaria may have contributed to the decline of the Roman Empire, and was so pervasive in Rome that it was known as the "Roman fever". Several regions in ancient Rome were considered at-risk for the disease because of the favorable conditions present for malaria vectors. This included areas such as southern Italy, the island of Sardinia, the Pontine Marshes, the lower regions of coastal Etruria and the city of Rome along the Tiber River. The presence of stagnant water in these places was preferred by mosquitoes for breeding grounds. Irrigated gardens, swamp-like grounds, runoff from agriculture, and drainage problems from road construction led to the increase of standing water.

The term malaria originates from Medieval Italian: mala aria—"bad air"; the disease was formerly called ague or marsh fever due to its association with swamps and marshland. The term first appeared in the English literature about 1829. 

Malaria was once common in most of Europe and North America, where it is no longer endemic,^[138] though imported cases do occur.^[139]

Malaria
A Plasmodium from the saliva of a female mosquito moving across a mosquito cell
Specialty	Infectious disease
Symptoms	Fever, vomiting, headache
Complications	Yellow skin, seizures, coma
Usual onset	10–15 days post exposure
Causes	Plasmodium spread by mosquitos
Diagnostic method	Examination of the blood, antigen detection tests
Prevention	Mosquito nets, insect repellent, mosquito control, medication
Medication	Antimalarial medication
Frequency	296 million (2015)
Deaths	730,500 (2015)

 

The signs and symptoms of malaria typically begin 8–25 days following infection; however, symptoms may occur later in those who have taken antimalarial medications as prevention. 

Initial manifestations of the disease—common to all malaria species—are similar to flu-like symptoms, and can resemble other conditions such as 

1. ·       sepsis, 
2. ·       gastroenteritis, and 
3. ·      viral diseases
4. ·       headache, 
5. ·       fever, 
6. ·       shivering, 
7. ·       joint pain, 
8. ·       vomiting, 
9. ·       hemolytic anemia, 
10. ·       jaundice, 
11. ·       hemoglobin in the urine, 
12. ·       retinal damage, and 
13. ·       convulsions.

Complications:

Malaria has several serious complications.

Among these is the development of respiratory distress, which occurs in up to 25% of adults and 40% of children with severe P. falciparum malaria. Possible causes include respiratory compensation of metabolic acidosis, noncardiogenic pulmonary oedema, concomitant pneumonia, and severe anaemia.

Although rare in young children with severe malaria, acute respiratory distress syndrome occurs in 5–25% of adults and up to 29% of pregnant women.

Coinfection of HIV with malaria increases mortality. Renal failure is a feature of blackwater fever, where hemoglobin from lysed red blood cells leaks into the urine.

Infection with P. falciparum may result in cerebral malaria, a form of severe malaria that involves encephalopathy. It is associated with retinal whitening, which may be a useful clinical sign in distinguishing malaria from other causes of fever

Enlarged spleen, enlarged liver or both of these, severe headache, low blood sugar, and hemoglobin in the urine with renal failure may occur. Complications may include spontaneous bleeding, coagulopathy, and shock.

Malaria in pregnant women is an important cause of stillbirths, infant mortality, abortionand low birth weight, particularly in P. falciparum infection, but also with P. vivax.

Diagnosis:

Malaria is usually confirmed by the microscopic examination of blood films or by antigen-based rapid diagnostic tests (RDT)

The sensitivity of blood films ranges from 75–90% in optimum conditions, to as low as 50%. Commercially available RDTs are often more accurate than blood films at predicting the presence of malaria parasites, but they are widely variable in diagnostic sensitivity and specificity depending on manufacturer, and are unable to tell how many parasites are present.

Classifications: 

Malaria is classified into either "severe" or "uncomplicated" by the World Health Organization (WHO). It is deemed severe when any of the following criteria are present, otherwise it is considered uncomplicated.

1. ·        Decreased consciousness
2. ·        Significant weakness such that the person is unable to walk
3. ·        Inability to feed
4. ·        Two or more convulsions
5. ·        Low blood pressure (less than 70 mmHg in adults and 50 mmHg in children)
6. ·        Breathing problems
7. ·        Circulatory shock
8. ·        Kidney failure or hemoglobin in the urine
9. ·        Bleeding problems, or hemoglobin less than 50 g/L (5 g/dL)
10. ·        Pulmonary oedema
11. ·        Blood glucose less than 2.2 mmol/L (40 mg/dL)
12. ·        Acidosis or lactate levels of greater than 5 mmol/L
13. ·        A parasite level in the blood of greater than 100,000 per microlitre (µL) in low-intensity transmission areas, or 250,000 per µL in high-intensity transmission areas

Preventions:

Methods used to prevent malaria include medications, mosquito elimination and the prevention of bites. There is no vaccine for malaria. 

Prevention of malaria may be more cost-effective than treatment of the disease in the long run, but the initial costs required are out of reach of many of the world's poorest people. There is a wide difference in the costs of control

Medication:

There are a number of drugs that can help prevent or interrupt malaria in travelers to places where infection is common. Many of these drugs are also used in treatment. Chloroquine may be used where chloroquine-resistant parasites are not common.

In places where Plasmodium is resistant to one or more medications, three medications—mefloquine (Lariam), doxycycline (available generically), or the combination of atovaquone and proguanil hydrochloride (Malarone)—are frequently used when prophylaxis is needed.

Doxycycline and the atovaquone plus proguanil combination are the best tolerated; mefloquine is associated with death, suicide, and neurological and psychiatric symptoms.

Treatment:

Malaria is treated with antimalarial medications; the ones used depends on the type and severity of the disease. While medications against feverare commonly used, their effects on outcomes are not clear.

Simple or uncomplicated malaria may be treated with oral medications. The most effective treatment for P. falciparum infection is the use of artemisinins in combination with other antimalarials (known as artemisinin-combination therapy, or ACT), which decreases resistance to any single drug component.

These additional antimalarials include: amodiaquine, lumefantrine, mefloquine or sulfadoxine/pyrimethamine.

Another recommended combination is dihydroartemisinin and piperaquine. ACT is about 90% effective when used to treat uncomplicated malaria.[64] To treat malaria during pregnancy, the WHO recommends the use of quinine plus clindamycin early in the pregnancy (1st trimester), and ACT in later stages (2nd and 3rd trimesters)

 

Compiled by: Dr. Sudhanshu Verma.