Tropical diseases and their globalization

Due to the fact that people all over the world are undertaking more and more long-distance journeys, pathogens that used to be restricted to one country can now appear globally.The latest examples proving this are SARS and the bird disease.Tropical and infectious diseases are by far the most frequent causes of death worldwide.They cause 41% of all deaths, far more than cardiovascular diseases.

in Germany, especially tropical diseases sometimes are not diagnosed in time because many physicians are lacking the required additional training and/or experience in this field.

Another problem in the treatment of tropical and infectious diseases is the increasing resistance of the pathogens to drugs.Besides development aid, the RDI pilot project, equipped with a tropical medicine laboratory and trained staff, provides a high-quality basis for medical science and research.Below you find a short outline of the most frequent diseases providing you, dear reader, with an overview of the tropical and infectious diseases which may also threaten you.

AIDS:

The Acquired Immune Deficiency Syndrom is a chronic, life-threatening immunity deficiency disease. The Human Immunodeficiency virus (HI virus) harms or destroys the immune system cells, making the body almost or completely unable to fight harmless infections. Also, the body becomes more susceptible to certain cancers.

Occurrence:The first AIDS cases became known about 20 years ago. Since, AIDS has developed into a global epidemic (see tables).

In 2004, 510,000 children alone died of AIDS worldwide.In Germany, about 44,000 people had AIDS in 2004, of which 34,000 were men, 9,500 women and about 300 children.

Infection: The HI virus is mostly transferred by sexual intercourse with infected partners, but can also be transferred by needles or syringes contaminated with infectious blood. Infected mothers can pass on the HI virus to their child during pregnancy, birth or breastfeeding.

Symptoms: 1. stage: 70 to 90% of all infected suffer from influenzal symptoms, swollen lymph nodes and rash 6 days to 6 weeks after infection.
2. stage: For 8 to 9 years, there are no symptoms or complaints. The virus, however, continues to multiply and destroys or damages the immune cells.
3. stage: About 40% of all infected suffer from lymph node enlargement.
4. stage: After about 10 years, the immune system is harmed to the extent that the following symptoms occur: night sweat, fever, diarrhea, dry cough and dyspnoea, weight loss and chronic fatigue. These symptoms are called HIV associated diseases. When pneumonia or certain types of cancer supervene, it is called „marked clinical picture of AIDS“.  Worldwide, tuberculosis is the most frequent HIV associated disease.

Diagnosis: By means of blood examination.

Therapy: Over the past years, many drugs have been developed for the treatment of HIV and the HIV associated diseases. In order to reduce the virus number in the blood, often 3 different drugs are given in combination. The problem is that those drugs have strong side effects, and the doctor is often walking a tightrope giving a high dose with a still bearable degree of side effects.  What is more, some drug resistances have already begun to develop lately.
As yet, there is no drug that can cure AIDS.

Malaria:

Malaria, also called marsh fever, is the most frequent tropical disease, caused by monocellular parasites of the Plasmodium genus.There are four pathogens that may harm humans: Plasmodium falciparum, Plasmodium vivax, Plasmodium oval and Plasmodium malariae.Plasmodium falciparum is the most dangerous among them for humans; without treatment, it leads to death in 30% of the cases.

Malaria is also described as a poverty disease, because mostly poor people with low spending power are affected by it. They cannot take any preventive measures and cannot afford medical treatment.

As yet, there is no vaccine protection against malaria. 

Occurrence:Malaria is a disease of the tropics and subtropics.In sub-Saharan Africa, Plasmodium falciparum predominates clearly over all other plasmodium types.Outside these regiona, the disease is imported by air travelers taking with them unintentionally an infected mosquito.

Worldwide, 300 to 500 million people fall ill with malaria each year.Every year, 1.5 to 2.7 million people are dying of malaria, half of them children under 5 years, and 90% of them Africans.In 2003, 3000 children under 5 years died of malaria each day in Africa.About 20% of the world's population are living in malaria infested regions.

About 900 malaria cases are reported in Germany each year, 3 to 8 of which die of this disease. About 87% of the German malaria patients had been in Africa before. 

Infection:Malaria is transferred by the bite of a female anopheline mosquito. The pathogens are transferred into the human blood with the mosquito's saliva and multiply within the human's liver cells.

Symptoms: Malaria often starts with sudden headaches and neck pains, shivering, heat discomforts and high fever. Thus, malaria is hard to distinguish from influenza. Only when there are rhythmic hot stages, differing in length depending on the pathogen, the type of malaria can be determined, except for malaria tropica (Plasmodium falciparum). In case of malaria tropica, the hot stages can occur unregularly or there can be no hot stages at all. Later, erythrocyte decomposition shows an anemia. Without treatment, malaria tropica can cause severe, usually lethal complications within the subsequent days, e.g. the "cerebral malaria", starting with dizziness and developing into coma in the end. In addition, the kidneys, the heart, the gastro-intestinal passage and the lung may be harmed.

Diagnosis: The most simple and quickest way is to detect the malaria parasites in the blood (thick drop) using a microscope.

Therapy: There are various drugs for the treatment of the several types of malaria. One has to be careful, however, since there are already some resistances in various malaria regions.

Prophylaxis: Travelers should inquire about the resistances in the countries they want to visit in advance (tropical medicine physicians or hospitals, public health agency).
There are various prophylactic drugs available in the pharmaceutical market, which, however, cannot provide a 100% protection against malaria infections.

Dengue fever:

Dengue belongs to the group of haemorrhagic fevers, i.e. fevers with bleeding tendency. This, however, does not occur in all cases.Dengue is a widespread virus infection in the tropics all over the world which millions of people fall ill with each year.

Occurrence:

Worldwide occurrence of the dengue fever

The infection occurs sporadically or epidemically in Southeast Asia, on the Indian subcontinent, in the Pacific area, in the Caribbean, in tropical Africa and in Latin America.According to WHO (World Health Organization) estimates, around 50 million people fall ill with dengue each year,and the numbers are increasing.

In the dengue infection areas, this disease is one of most frequent causes of deaths among infants. Hundreds of thousands of cases take the severe haemorrhagic form which 20,000 people die of every year.

Long-distance travelers are increasingly importing dengue also to Germany. In 2001, 231 cases became known in Germany.

Infection: The dengue virus is the pathogen of this disease. The natural reservoir of the pathogen is the human body. By biting, various mosquito species spread the pathogen among humans.

Symptoms: There are 3 different forms of the disease: 1. Classical dengue fever:  Begins with influenzal complaints as e.g. high fever, shivers, conjunctivitis, headaches and limb pains, circulatory distress and diarrhea. These first complaints may be very violent. Soon, the fever drops rapidly, and rises again after one or two days. In this stage, the pathogens can be detected in the blood using special methods. 2. Mild, atypical form: The symptoms are similar to the classical form, only milder and shorter. 3. Dengue haemorrhagic fever or dengue shock syndrome: This clinical picture often occurs with children or if it is the second infection caused by a different virus type. After the first phase of the disease as described above, there are one to three afebrile days, followed by another attack. In addition to the high fever, there is now internal haemorrhage, revealed by bloody vomit and sometimes bloody diarrhoea. In case of massive bleeding, a shock can occur which is usually fatal.  6 to 20% of the patients with this severe clinical picture die, and they are mostly small children.

Diagnosis:Pathogens are detected in the blood.

Therapy:There is no special therapy against dengue yet.The therapy employed is a symptomatic therapy.

There is no vaccine against the dengue virus.

Marburg Fever:

This is also a virus-related haemorrhagicfever, i.e. a fever with a tendency for bleeding, originating from the African rainforest. The Marburg virus is quite similar to the Ebola virus and thus also is its course of disease. The name results from its first appearance in the German city of Marburg in 1967.

Occurrence: When this kind of fever appeared in 1967 for the first time, 31 people in Germany and Yugoslavia were affected, of which 7 people died. The infection originated in Africa, mainly in Uganda, West Kenya and Zimbabwe.

Spreading of the Marburg virus in 2005 in Angola.

In March 2005 the Marburg virus was discovered in several fatalities in Angola. And in April this disease already spread on 7 of Angola’s provinces. Until then 215 people died due to this disease, mainly children under the age of 5. From 1998 to 2000 a total of 149 people were infected in DR Congo and a total of 123 people died as a result, whereas from October 2004 to May 2005 388 people were infected in Angola and a total of 324 people died.

Infection: Despite many years of research the natural reservoir (reservoir host) of the Marburg virus is still unknown. Assumingly this virus is breeding in bats, birds or/and insects. The virus is mainly communicated via the blood, which is highly infectious, but also through other body fluids like „airborne infection” by being coughed at, by perspiration and even by tear fluid.

Symptoms: Approx. 5 – 9 days after infection one suffers from flue-like discomforts (see malaria). Therefore the Marburg fever is hard to distinguish from a malaria infection at the beginning. In the following one suffers from vomiting and from aqueous diarrhoea. In the further course also internal bleedings appear. Due to the high dehydration the people infected may painfully die within only a couple of days. Children under the age of 5 are the major victims of this infection.

Diagnosis: The Marburg virus can be isolated by an electron microscope in the blood, but also from organs and tissues.

Therapy: For the time being there is no drug available against the Marburg virus. Therefore therapy is limited to treatment of the symptomatic conditions by replacement of fluids, pain therapy, staying in bed, etc.
No vaccine against the Marburg fever is available yet.

Ebola:

Ebola also belongs to the group of the haemorrhagicfevers and is quite similar to the Marburg fever.

Occurrence: In Zaire and in Sudan approx. 602 people were infected in 1976; 430 people died. In 1979 another 34 people were infected in Sudan; 22 of them died. In 1994 44 people were infected in Gabon; 28 died. In 1995 315 people were infected in Zaire; 244 of those died. Up to October 2001 approx. 1,479 people on the African continent were infected with the ebola virus and approx. 988 people thereof died as a result of this disease.

Infection:  Despite many years of research the natural reservoir (reservoir host) of the Ebola virus is unknown. Infection is the same as for the Marburg fever (see above).

Symptoms: Approx. 9 – 16 days after infection similar symptoms as for the Marburg fever (see above) appear. Additional symptoms are bleedings of skin and mucous membrane because the infection spreads across the whole organism and destroys also the smallest blood vessels (capillary vessels). Particularly bleedings in the stomach-intestines channel, in the lungs and in the spleen are fatal.

Diagnosis:

Microscope shooting of the Ebola virus.

The Ebola virus can be detected in the laboratory in blood, saliva and urine. 

 
Therapy: For the time being there is no particular drug against the Ebola virus. Therefore therapy is limited to treatment of symptomatic conditions.

No vaccine against Ebola is available yet.

Cholera:

Cholera is a serious bacterial and infectious disease that mainly affects the small intestine. If not treated, the death rate for people infected with cholera is at 60 %.

Occurrence:

Worldwide cholera occurrence

In 1992 a total of 761,783 people in 68 countries were reported to be infected with cholera; 8,000 of those people died.

Infection: The cholera bacteria reach the human gastrointestinal tract through bowel movements, polluted water, or in rare cases also through polluted food.

Symptoms: The outbreak of the disease is after 2 – 3 days after infection. The course of this disease usually has 3 stages: First stage: diarrhoea and sickness; the liquid diarrhoea contains mucus flakes (rice water stool). Bellyache can rarely be observed. The second stage is dehydration (exsicosis). The patient suffers from insufficient temperature and shows a striking facial expression with a pointed nose and sunken cheeks as a result of dehydration. If the skin folds are lifted they remain standing. The third stage shows general body reactions like fever, drowsiness, confusion, and coma and skin rash.

Diagnosis: Bacteriological proof of bacteria in the stool.

Therapy: Replacement of lost fluid by application of saline-sugar solutions, which is the most important and first measure to take. In case of a severe course of disease also antibiotics should be applied.
Thanks to this measure the death rate could be reduced from more than 60 % to less than 1 %.

A vaccine against cholera is available.

Yellow fever:

Yellow fever is also called black emesis and is an acute and feverish viral infection. This disease also belongs to the group of haemorrhagicinfections (see above).  Originally this disease was detected in Africa only.

Occurrence:

Worldwide

In the tropical and subtropical areas of South America and Africa. From 1985 to 1996 23,540 cases of yellow fever were registered; 6,420 of those resulted in death. However, a much higher amount of yellow fever cases are assumed as there might be a possibility that not every case was reported. In October 2001 203 people were infected with yellow fever and 21 of these died. A mass vaccination of 2.6 million people within only a couple of days and in due time prevented an epidemic. There are approx. 200,000 diseases each year and 30,000 cases of death, 90 % thereof in Africa alone.

Infection: The yellow fever virus is passed on by the sting of the yellow fever mosquito.

Symptoms: This disease may have very different courses, from light cases that hardly can be diagnosed to really severe cases with a death rate of 50 %. 1 - 2 days after infection the patient suffers from fever, shivering, headache and limb pains, a slower pulse, nausea, vomiting, all of which may ease off after a few days. About 15 % of the infected people will enter into the second stage of this disease showing an increase of fever, swelling of the liver, icterus and vomiting of blood.

Diagnosis: This disease is mainly diagnosed during the second stage due to the disease pattern. Additionally also the yellow fever virus can be detected in the blood.

Therapy: As there is no specific drug against this virus available, only the pathology of yellow fever can be treated.

However, a well tolerated and really effective vaccine is available.

Sleeping sickness:

The sleeping sickness is a tropical infection resulting from parasites. It is divided into 2 different types of pathogenes:
1)     The trypanosoma brucei gambiense as the pathogen for the West African sleeping sickness.

2)     The trypanosoma brucei rhodesiense as the pathogen for the East African sleeping sickness.

Occurrence: Mainly in tropical Africa, i.e. wetlands such as courses of rivers and swamplands. However, it can also be found in dry savannahs like the Kalahari. More than 50,000 people are affected by the sleeping sickness. Tendency increasing.

Infection:

The tsetse fly is the carrier of the sleeping sickness. Together with the fly’s saliva the pathogen reaches the human body. The sting really hurts and can even pass thick clothes. With one sting only a couple of thousand pathogenes enter the human body. The infection risk as a result of such a sting of the tsetse fly is at a ratio of 1:100. Humans, domestic pigs, specific types of rats and mice and the antelope are the parasites’ reservoir of the pathogen for the West African sleeping sickness. For the East African sleeping sickness additional parasites’ reservoirs are bushbucks, domestic cattle, the African buffalo, spotted hyenas and lions.

Symptoms: The course of the West African sleeping sickness is slower and less distinct than the East African version.

First stage: After approximately one week a painful swelling and vesicles appear at the puncture. However, this only happens for approx. 5 – 20 % of the people infected. After a period of 2 – 3 weeks the patient shows fever and shivering, headache and limb pains, fluid retentions, itching, the skin starts to change and also swellings of the lymph nodes.
Second stage: After a period of approx. 4 – 6 months – a little earlier in case of the East African sleeping sickness – the pathogenes get into the central nervous system.

This results in the patient suffering from confusion, ataxias and insomnia as well as cramps.

In the final stage the person infected is semi-somnolent. Hence the name of this disease.  

Diagnosis: In the first stage the pathogen can be detected in the blood when tested under the microscope (thick drop), or in the lymph node tissue by taking a specimen out of it. To rule out the second stage, brain fluid is tested for pathogenes.  

Therapy: Drugs are applied in the first stage, which do not cross the blood-brain-barrier. However, due to the high toxicity of these drugs treatment is made in hospital in most of the cases. Drugs with arsenic solutions are applied as soon as the patient has reached the second stage. These drugs affect the central nervous system and can also have severe side effects. Death rate is at approx. 5 %.

We do not know whether there are preventive drugs available to protect oneself against this sleeping illness. Up until 2004 there were none on the market.

With these eight brief examples we tried to make you aware of the importance of both, medical aid with regard to tropical infection diseases and the scientific research on this field, for the people affected as well as for the people in Germany.