Clinical characteristics of some tropical infections with hemorrhagic manifestations presents in tropical South America
During the past 20 years there has been a dramatic emergence and re-emergence of epidemic of haemorrhagic vector-borne-disease (VBD) that have been caused by viruses believed to be under control such as dengue, yellow fever, Venezuelan equine encephalitis, Saint Louis Virus, Arenavirus, hantavirus or viruses that have extended their geographic distribution such as West Nile and Rift Valley fever. Bacteria like
Many reports have demonstrated the changing global and tropics epidemiology. The population growth, urbanization, human activities, and even climate variability all help to a continual fluctuation in the epidemiology of several haemorrhagic fevers transmitted by vectors in the tropics.
Haemorrhagic fevers produced by bacterial or virus share many general features. Those infectious agents are arthropod-borne cause many haemorrhagic fevers. For some viral haemorrhagic fevers, person-to-person transmission may occur through direct contact with infected blood or secretions. Infectious agents are transmitted by arthropod like mosquitoes and ticks. Animal reservoirs are usually wild rodents, however, pets, domestic livestock, urban mice, monkeys, and other primates may also provide as intermediate hosts.
The term viral hemorrhagic fever describes a potentially fatal clinical syndrome characterized by an insidious onset of nonspecific signs followed by bleeding manifestations and shock. The haemorrhagic fever syndrome is also characterized by a combination of a capillary leak syndrome and bleeding diathesis. The clinical manifestations and even histopathological findings are pretty similar and difficult to make a differential diagnosis (Table 1, Figure1). In the tropics where endemic haemorrhagic fevers are frequent that is a big concern.
This chapter gives an overview of the epidemiology and ecology of haemorrhagic fevers transmitted by vector taking place exclusively in the neotropics, hence it shows the principal clinical syndromes associated to vectors.
2. Common VBD in the tropics transmitted by arthropods and rodents
Etiological agents of HF affect humans on all continents. Most but not all agents causing HF are arboviruses, with transmission to humans resulting from an arthropod bite. However, animal reservoirs are generally rats and mice, but domestic livestock, monkeys, bats and other primates may also serve as intermediate hosts. Population growth, urbanization, human activities, and even climate change all contribute to a continual flux in the epidemiology of many HF transmitted by vectors arboviruses.
Haemorrhagic fevers share many clinical common features. Infectious agents that are arthropod-borne (usually mosquitoes and ticks) cause many viral hemorrhagic fevers. Some viral hemorrhagic fevers, person-to-person transmission may occur through direct contact with infected patients, their blood, or their secretions and excretions.
3. Flaviviral hemorrhagic fevers
Dengue is the mainly significant arboviral disease of humans with over half of the world's population existing in areas of risk. The occurrence and scale of epidemic dengue have augmented considerably in the last 40 years as the viruses and the mosquito vectors have both extended geographically in the tropical regions of the world in particular across South-east Asia, Africa, Western Pacific and tropics areas of the Americas, (Figure 2).
Dengue and Yellow fever are the prototype virus of the
Dengue fever is supposed to generate about 230 million infections worldwide every year, of which 25,000 are lethal. Worldwide incidence has increasing swiftly in new decades with some 3.6 billion people, over half of the world's population, currently at risk, primarily in cities and villages centres of the tropics and subtropics. Demographic and community changes, in particular urbanization, globalization, and augmented worldwide journey, are most important contributors to the get higher incidence and geographic extension of dengue infections.
In modern lifetimes, the proliferate of unprepared urbanization, with related unsatisfactory housing, overcapacity and weakening in water, sewage and waste management systems, has produced model circumstances for enlarged diffusion of the dengue virus in tropical urban areas. Age frequency of dengue has been distributed in a broad ages either in adolescents or adults. In addition, the advance of tourism in the tropics has led to a boost in the number of tourists who become infected, mainly adults.
Symptoms and risk factors for dengue haemorrhagic fever (DHF) and severe dengue differ between children and adults, with co-morbidities and incidence in more elderly patients associated with greater risk of mortality. Treatment options for DF and DHF in adults, as for children, centre round fluid replacement (either orally or intravenously, depending on severity) and antipyretics. Further data are still needed on the optimal treatment of adult patients.
Because Dengue is endemic in the most tropical countries, the disease is overdiagnosed, therefore, many other hemorrhagic fevers as leptospirosis, hantavirus, arenavirus, rickettsiosis, Venezuelan equine encephalitis, chikungunya virus and malaria are erroneously diagnosed as dengue. Those diseases are clinically indistinguishable from dengue and other vector borne diseases and confirmatory diagnosis needs the employ of proficient laboratory tests that are difficult to pay for developing countries. Consequently, the endemic diseases above mentioned in developing countries remains mostly unidentified. Recent surveillance suggests that Venezuelan equine encephalitis, it may represent up to 10% of the dengue burden in neotropical cities, or tens-of-thousands of cases per year throughout Latin America.
On the other hand, yellow fever remains an important cause of mortality and morbidity in several South American countries like Colombia, Venezuela, Guyana, Ecuador, Peru, Bolivia and Brazil (Figure 2). The mosquitoes of
YF has two different cycles: one endemic or sylvan cycle involving monkeys and epidemic urban cycle rare in South America. The frequented endemic sylvan YF constitutes to great source for introducing into urban environment. Despite the serious public health that YF represents, many South American countries abruptly discontinued YF campaigns.
The hantaviruses are a group of emerging rodent-borne pathogens (family
Patients with HCPS typically present a short febrile prodrome of 3-5 days. In addition to fever and myalgias, early symptoms include headache, chills, dizziness, non-productive cough, nausea, vomiting, and other gastrointestinal symptoms. Malaise, diarrhoea, and lightheadedness are reported by approximately half of all patients, with less frequent reports of arthralgias, back pain, and abdominal pain. The mean duration of symptoms before hospitalization is 5.4 days. Remarkable hematologic result included a high white-cell count with augmented neutrophils, myeloid precursors, and atypical lymphocytes.
Several characteristics distinguish Latin American HCPS cases from the classical HCPS described for the first time in the USA. These include a variation in severity of disease from moderate and self-limiting to severe, the demonstration of person-to-person transmission, and a somewhat higher incidence of extrapulmonary clinical manifestations in the South American form of HCPS. Nevertheless, hantaviruses in the Americas is still far from complete knowlodgement. The factors involved in the dynamics of these viruses in nature, their establishment and transmission within host populations and from hosts to humans, and the variable pathology of these viruses in humans are complex. It is likely that more hantaviruses will be described in the future, and much more data will be required in order to describe the diversity and evolution of this group of pathogens. Latin America, as the centre of diversity for
The recognized arenaviruses in the Americas are hosted by rodents of the family
6. South American hemorrhagic viruses
Four members of the Tacaribe complex produce acute disease in humans: Junin, Machupo, Guanarito, and Sabiá viruses. Junin virus, the mainly considerably studied of the South American hemorrhagic fever viruses, is the agent of Argentine hemorrhagic fever. The disease disproportionately affect men, probably because of the job-related risk linked with agricultural work. The mouse
Guanarito virus, the agent of Venezuelan hemorrhagic fever, mainly affects rural populations and has a restricted geographic circulation. Venezuelan hemorrhagic fever has been described close to the Portuguesa province in northwestern Venezuela, an intensively agricultural area. In 1989, previous to its detection as a dissimilar an hemorrhagic disease, irregular cases of Venezuelan hemorrhagic fever were probably mistaken diagnosed as dengue fever. Remarkably, deforestation and human intrusion into rodent environment may have resulted in augmented human contact to infected rodents and a concurrent enhance in human illnesses. The reservoir of Guanarito virus is a short-tailed rodent called
Regarding Bolivian hemorrhagic fever, Machupo virus is considered the etiology agent, which it was discovered in 1962 during an outbreak of viral hemorrhagic fever. Outbreaks of Bolivian hemorrhagic fever have occurred in cities and towns, probably connected to factors that privileged the invasion of human dwellings by rodents. Good practices control of outbreaks was capable through execution of intensive rodent trapping and education programs. The reservoir of Machupo virus is a sunset mouse
Regarding Brazilian hemorrhagic fever, Sabiá virus, is recognized as the etiologic agent. Sabiá virus was detected in 1994 from a Brazilian patient who was originally believed to have yellow fever, at that moment, a viral hemorrhagic fever was diagnosed. After that, no cases of acquired human disease caused by Sabiá virus have been reported. The reservoir of this virus is unknown, but is assumed to be a South American rodent. Sporadic cases of infections with Sabiá virus was been reported among laboratory workers in Brazil and the United States.
Arenavirus cases in Colombia have not been reported yet. However, we collected and tested 210 sigmodontine rodents of 3 species: 181
Besides the hemorrhagic South American virus described above, the principal old world arenavirus are the Lymphocytic choriomeningitis virus (LCMV) and Lassa virus. LCMV has a global spreading, which coincides with the geographic dispersion of its major host, the ever-present house mouse (
In Europe and USA, peaks in the summer and fall are likely because more mice are entering homes. It is really unknown the incidence of infection in humans in different countries with lymphocytic choriomeningitis virus, but mainly experts believe the disease is not well known or underrecognized or underreported. The seroprevalence of lymphocytic choriomeningitis in different countries is between 0% and 60%. Vague clinical signs, demanding diagnostic problems, because require of knowledge on physicians and public health workers to put together recognition of lymphocytic choriomeningitis virus infections and its role diseases in humans.
Regarding Lassa fever is a significant cause of febrile disease in West Africa; it is projected about 100,000 to 300,000 cases and numerous deaths linked to Lassa virus. The cases are primarily reported from hyperendemic or endemic foci in the West African countries of Guinea, Liberia, Nigeria, and Sierra Leone.
It is a bacterial zoonotic disease that affects both humans and animals. Humans become infected through direct contact with the urine of infected animals or with a urine-contaminated environment.
There are 20 known
Outdoor and agricultural workers (rice-paddy and sugarcane workers for example) are particularly at risk but it is also a recreational hazard to those who swim or wade in contaminated waters. In endemic areas the number of leptospirosis cases may peak during the rainy season and even may reach epidemic proportions in case of flooding because the floods cause rodents to move into the city.
Prevention strategies of human leptospirosis include wearing protective clothing for people at job-related risk and evading of swimming in water that can be polluted. Leptospirosis control in animals dependent on the serovar and animal species, the management infection can be done by vaccination and rodent controls (24, 26).
In Latin America, several
In Colombia, Rocky Mountain Spotted Fever (RMSF) was first reported in 1937 by Patino. It was named Tobia fever because of the village where these cases occurred. The disease remained forgotten until 2003, when two fatal cases were identified and reported in Villeta, a locality next to Tobia. More recently, three outbreaks of RMSF have occurred in Colombia: in 2006 among military personnel in Necocli (Antioquia), in 2007 in a township of Los Cordobas (Colombia) and in 2008 in Altos de Mulatos (Antioquia). These reports defined the reemergence of the disease in Colombia and alerted the systems of surveillance across the country.
A total of 10
The etiologic agent of malaria is a parasite denominated
In the human body, the parasites reproduce in the liver, and then infect red blood cells. Symptoms of malaria consist of fever, headache, and vomiting, and usually show between 10 and 15 days after the mosquito bite. If not treated, malaria can rapidly turn into life-threatening by disturbing the blood provide to vital organs (30). In Africa and Latin America, the parasites have showed resistance to a several of malaria medicines. Means interventions to control malaria include: prompt and effective drug treatment; apply of insecticidal nets by people at risk; indoor residual spraying with insecticide to manage the vector mosquitoes, transgenic mosquitoes manipulated for resistance to malaria parasites and biological control of mosquitoes.
Malaria remains one of the world's serious health problems with 1.5 to 2.7 million deaths yearly; these deaths are mainly among children and pregnant women in sub-Saharan Africa. Of connotation, more people are dying from malaria today than 30 years ago. It seems to be the vector, the female anopheline mosquito is changing its behaviour or adapting to human activity such as creating new mosquito breeding sites. Hence, the impact of augmented population, and people displaced by violence can boost the incidence and proliferation of malaria. Furthermore, the difficulty of drug resistance by the parasites to almost all currently available antimalarial drugs.
Finally, most of the hemorrhagic tropical diseases describe above, can be also classified as neglected tropical diseases. Those represent some of the most common infections of the poorest people living in developing countries. Because they primarily affect the marginalized poor as well as preferred indigenous populations and people of African descent, the tropical hemorrhagic diseases in the Latin American and African countries are predominantly ignored diseases.
There is also misdiagnosis of hemorrhagic diseases in the tropics, mainly because the weak epidemiology and public health system in developing countries. The maximum disease problem of hemorrhagic diseases, such as leptospirosis, rickettsiosis, malaria and hantavirus infections, have first require scale-up of accessible funds or the advance of new measures instruments in order to accomplish control (32). The total elimination is implausible in the tropics, for that reason require and inter-disciplines efforts as social services, community education and environmental interventions.
The tropical hemorraghic fevers in the neotropics is a group of debilitating viral, bacterial and parasitic infections, that are very common aetiology of illness of the poorest people living in developing countries as Latin America. During the past 20 years there has been an intense emergence and re-emergence of epidemic of haemorrhagic vector-borne-disease (VBD) that have been produced by viruses supposed to be under control such as dengue, yellow fever, Venezuelan equine encephalitis, Saint Louis Virus, Arenavirus, hantavirus or viruses that have prolonged their geographic distribution such as West Nile and Rift Valley fever. Bacteria like
To Dr. Juan Carlos Lozano, MD, for the cooperation and helpful in the design of Table 1.