University of Washington Department of Health Services Vector-Borne Emerging Disease

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INDEX Overview of Emerging Vector-borne Infectious Diseases Parasitic Diseases Bacterial Diseases Lyme Disease Plague Viral Diseases Japanese encephalitis Kyasanur Forest Disease Yellow Fever Dengue Fever Changing Epidemiology of Hemorrhagic Fever Dengue in the Americas Dengue in the United States Distribution of Dengue in Africa Economic Impact of Dengue in Puerto Rico Factors Responsible for Emergence/Resurgence of Vector-borne Diseases Demographic Changes Societal Changes Genetic Changes in Pathogens Deteriorating Public Health Infrastructure Climate Change Prospects for the Future Questions & Answers Readings Overview The popular press drives a lot of what we're seeing. By creating publicity, which helps us get the support we need for our programs, the press is actually very helpful to us. However, the hype they create makes it seems that we're always responding to a crisis. If you look at just a sampling of epidemic infectious diseases that occurred in the 90's, you will find that a good share are vector-borne diseases: Dengue Yellow Fever, Venezuelan encephalitis. Malaria is one of the most common parasitic diseases, but it does not really occur in major epidemics. The bulk of these infectious diseases are caused by viruses; most people do not appreciate that a good percentage of epidemics that occur globally are caused by vector-borne diseases. 1) Parasitic Diseases emerging or resurging in the last eight years Malaria has increased in the Amazon region of South America and Korea and is a problem in Africa. Cases of locally transmitted malaria have increased in the United States. All are isolated incidents, but still it is a reflection of the increased importation of malaria into the United States. Malaria is the biggest problem regarding vector-borne parasitic diseases. Leishmaniasis in Africa and India. African Tryponosomiasis is a major problem in Africa. 2) Bacterial Diseases With the exception of plague, there have not been major epidemics of bacterial diseases. Parasitic and bacterial diseases essentially cause a high incidence but not major epidemics. 1) Parasitic Diseases emerging or resurging in the last eight years 2) Bacterial Diseases With the exception of plague, there have not been major epidemics of bacterial diseases. Parasitic and bacterial diseases essentially cause a high incidence but not major epidemics. [SLIDE] In the western hemisphere, we have continued outbreaks of Tularemia; tick-borne relapsing fever in Spain and Italy; Erlichiosis, a new emerging disease; Lyme disease, a newly emergent disease in the last 20 years; Plague outbreaks occurred in Peru, China and various places in Africa; louse-borne typhus epidemic in Burundi in 1997 Lyme Disease The global distribution of Lyme disease is essentially the same as the distribution of the tick vectors. Ixodes recinis ticks, are basically a temperate species of the Ixodes genus.. Lyme disease was first described in the US in 1975. CDC started surveillance in 1982, and over the past 15 years there has been a dramatic increase in reported cases of Lyme disease. That may be a surveillance artifact, reflecting increased awareness and increased reporting. When we support active surveillance systems in a particular area to try to find out how much Lyme disease occurs, we see a dramatic increase in the reported cases. However, we’re convinced that this increase is real. We’re seeing a geographic spread of the ticks and the spirochete that causes Lyme disease, and with that increased numbers of cases. A lot of it has to do with habits of the people. 80 or 90% of reported cases occure in the upper Atlantic states, the upper Midwest, and California; almost identical to the geographic distribution of the tick vector in the United States. In this area the highest endemnicity is associated with residential transmission. People are being infected in their back yards. Ixodes scapularis is the main vector in the Northeast and upper midwest. [Slide: The areas in red are Ixodes scapularis, reported Ixodes scapularis is in blue] The eastern half of the United States has Ixodes scapularis. So why do we see all the Lyme disease in the northeast and not elsewhere? This is a major question associated with Lyme disease that we’re trying to deal with right now. The Ixodes scapularis in the southern part of the United States is a biologically distinct tick. It is not as good a vector and has different host feeding patterns. Although it is occasionally naturally infected with Borrelia burgdorferi, we do not think the spirochete that causes Lyme disease is involved in transmitting the disease in the lower part of the United States. There is a Lyme-like disease that may be caused by another spirochete. This is one of the major problems we’re trying to focus on with our Lyme disease program. The principal reservoir hosts are mice. Ixodes dentatis is the tick species that is probably involved in the maintenance cycle of Borrelia burgdorferi in the southern United States. In California, it is Ixodes pacificus, which is very closely related.. This Slide simply shows the areas in the upper Atlantic northeastern states that have the high incidence... 30 or more cases per 100 thousand in red, 10 to 29 cases in green and 5 to 9 cases in yellow. These are primarily associated with what we call the Ixodes scapularis, the vector of Lyme disease. Plague Plague is a very old disease. The last pandemic of began at the turn of the century when it was introduced into the United States. Plague in the US The western half of the United States has plague. Every continent with the exception of Australia has enzootic areas where plague is maintained. We do not know a lot about the reservoir hosts and the natural transmission cycles of plague. In the United States, we do not even know which are the true maintenance reservoir hosts for this bacillus. This slide is the confirmed cases of plague in the United States from 1970 through 1997. We’re not sure why we have little outbreaks every few years. Some people have associated it with the El Niño years and climatological changes. However plague is not a major public health problem in the United States and over the years CDC has decreased its plague program. We have 10 to 15 cases on average every year, sometimes 1 to 3 deaths, mainly because physicians do not consider plague in the differential diagnosis from non-enzootic areas. We have a WHO collaborating center for reference and research in Fort Collins for plague. Epidemic Arboviral Diseases Many of the epidemics around the world are vector-borne viral diseases. These are epidemics which occurred from 1990 to 1997. Epidemic arboviral diseases are a global public health problem. Dengue, like malaria, has a global distribution in the tropics. Dengue is the most important arboviral disease. There are four of these viruses that are capable of causing major epidemics in humans. Humans, when they are infected, have high viremia, so that there is person to person transmission via mosquito vectors. Japanese Encephalitis Japanese Encephalitis is an Asian disease. This Slide is the approximate distribution of the virus with the reported numbers of cases that have occurred in recent years. There is a licensed vaccine available, but it is not yet widely used. Only a few countries put it in the EPI ( expanded program of immunizations). In the past 5 or 6 years, we have actually seen an expanding geographic distribution of Japanese Encephalitis; we’re not sure why. We have seen it move into the Philippines, Nepal and SW India, and the northern Mariana Islands in the 1970’s and 80’s and into Australia in the 1990’s. Japanese Encephalitis in Torres Strait An outbreak occurred in 1995 in Badou Island, Torres Strait, Australia. Japanese Encephalitis is very closely related to an Australian virus called Murray Valley Encephalitis. It was always thought that Murray Valley Encephalitis was east of Wallace’s Line and Japanese Encephalitis was west of Wallace’s Line. This all changed in the last couple of years with this epidemic that occurred in Badou Island.. This was the first documented outbreak in the history of Australia. We do not know where it came from, but it was probably introduced from Papua New Guinea. The principal vector of Murray Valley Encephalitis, Culex annulirastasis, was the likely vector in Torres Strait. There was transmission again in 1996 suggesting that this area now has become enzootic for Japanese Encephalitis. Japanese Encephalitis in Nepal In the 1950’s and 60’s, USAID essentially eradicated maleria from this whole area and opened it up for agriculture. They cleared the forest and replaced it with paddies that propagated Culex mosquitoes. So they got rid of malaria, but Japanese Encephalitis was introduced in 1978. The first epidemic of Japanese Encephalitis in Nepal occured in 1978. You can see what has happened. There are epidemics every 2 to 3 years, each one getting progressively larger. In 1997,there was the largest epidemic on record in Nepal. The epidemics began in the eastern part of the country and moved west. That is why you see the expanding geographic distribution associated with increased numbers of cases. We’re not sure what the ecology of Japanese Encephalitis is in Nepal. We assume that it has a natural history similar to other parts of Asia, but there has not been any work done in that area. Kyasanur Forest disease Another very interesting disease is Kyasanur Forest-like disease in Saudi Arabia. In 1994, they was a lot of construction in Jedda, Saudi Arabia, and the Aedes aegypti was introduced into the construction sites. They had a major epidemic of dengue with sporadic cases of dengue hemorrhagic fever in Jedda in 1994. They were actually doing surveillance for viral hemorrhagic fever, looking specifically for dengue and Congo Crimean hemorrhagic fever when they found a flavi virus that didn’t grow in the mosquito cells. We identified it, by the genetic sequencing of the envelope protein, as a Kyasanur Forest disease virus. Kyasanur forest disease is a virus that is found primarily in the forests of south India in Mysore. It primarily affects monkeys. Humans are affected when they go into the forest. They have had epidemics of hemorrhagic fever, but it not associated with desert areas like Jedda. It turns out that there was actually another case in 1994 and we have now six isolates, all from butchers. Four additional cases were diagnosed serologically. All of the people who had confirmed infection were somehow associated either with slaughterhouses or sheep. We did electron microscopy on these viruses and could tell that they are classical flaviviruses. When we sequenced both the Envelope gene and the NS-5 gene we could see it is closely related to Kyasanur Forest disease virus. We do not think it is Kyasanur Forest disease, but probably a very closely related virus in the tick borne group that has somehow been introduced into the Middle East. Yellow Fever Global Distribution of Yellow Fever Yellow Fever is a major resurgent disease, primarily in Africa. This is despite having a very effective and safe vaccine. This is the global distribution of yellow fever, seen in the northwestern half of South America and the central part of Africa. Yellow Fever is probably an African virus that was introduced into the Americas during the slave trade. In the 1950’s they implemented a control program in the Americas. It utilized both mosquito eradication and yellow fever vaccination. In Africa, most of the emphasis was on vaccination. Most of the resurgence in the past 10 years has occurred in West Africa, however there was an epidemic of yellow fever in Kenya for the first time in history in 1990 and 1993. Yellow Fever in the Americas Aedes aegyptiis the principal vector of yellow fever. Note the approximate distribution of Aedes aegypti in the Americas in the 1930’s. An eradication program was implemented in 1947, and by 1970, they had eradicated the mosquito from all of Mexico, Central America and most of South America with the exception of the Guyanas, Venezuela and the Caribbean Islands south of the United States. In the 1970’s they made a decision to disband the Aedes aegypti eradication program. Aedes aegypti began re-invading these countries from areas that had not achieved eradication. Potential Spread of Urban Yellow Fever If we start seeing urban epidemics of yellow fever in the Americas, we feel that it is going to quickly spread to the Pacific and Asia. The other major issue is that we’re not using the vaccine effectively in the EPI program. These yellow dots represent urban epidemics of yellow fever in the 1930’s and the early 1940’s, the red dots here indicate epidemics of dengue in the 1980’s and the 1990’s. These are shown relative to the distribution of Aedes aegypti the 1930's and the 1990's The concern is we could see urban yellow fever spreading to all major centers in the Americas, similar to what happened with dengue virus. When that happens people can get on airplanes and fly directly to the Asia-Pacific with the potential of bringing yellow fever into this region. Why urban yellow fever epidemics have not ever occurred in Asia is one of the great unanswered virology questions. One reason may be that the virus is rarely introduced into the region. Second, some cross-protective immunity may exist which does not protect against yellow fever infection but may modulate the infection. The heterotypic flaviviruses in Asia may down-regulate Aedes aegypti infections so that the viremias are lower, decreasing the probability of mosquitoes becoming infected in secondary transmission. Dengue Fever Historical— Dengue and dengue hemorrhagic fever (DHF) are caused by four dengue viruses. There is no cross-protective immunity among these viruses. A person can have as many as four infections during their lifetime when they live in an endemic area. It is transmitted by Aedes aegypti, the same mosquito that transmits yellow fever in an urban situation. The urban ecology of dengue and yellow fever are identical. We have seen a dramatic resurgence of dengue and the emergence of dengue hemorrhagic fever in the past 15 to 20 years. We have seen increased epidemic activity on a global basis in the tropics and expanding geographic distribution, both of viruses and the mosquito vectors. We have seen the development of hyperendemicity, which is most closely associated with the emergence of dengue hemorrhagic fever. Hyperendemicity means that there are multiple virus serotypes co-circulating in the same community. Once you start seeing hyperendemicity in a community, it is not long before the first cases of dengue hemorrhagic fever begin to occur. The geographic expansion of epidemic dengue hemorrhagic fever is shown from 1950 through 1997. Changing Epidemiology of Hemorrhagic Fever During the decade of the 1970’s DHF began its geographic expansion, moving into Burma and Indonesia. From 1980 to the present time, we have seen a more dramatic geographic expansion with movement into India, Pakistan, the Maldives Islands, Sri Lanka, and China. The surveillance for this disease is very poor. Dengue typically gets reported as malaria. Resurgence in Singapore Singapore, which has had one of the most effective prevention and control programs in the world, had a dramatic resurgence of epidemic dengue and dengue hemorrhagic fever beginning in 1986. This appears to be attributable to the retirement of the person in charge of the program and lack of a replacement. In 1996 there were more cases reported than they have ever had in the history of Singapore. Emergence of DHF Dengue in the Americas and the Emergence of Dengue Types I-IV During the 1950’s, 1960’s, and 1970’s, dengue was rare in the American region; only an occasional epidemic occurred in the Caribbean areas. With the disbanding of the Aedes aegypti eradication program and the re-invasion of tropical America by Aedes aegypti in the 1980’s, we began to see the resurgence of epidemic dengue.   Click on image to enlarge This shows the number of American countries with epidemic dengue by decade with a low point in the 60’s. Aedes aegypti began to reinvade Mexico in 1970., A new virus type, dengue type 1, was introduced into the region. In the 1980’s, two new viruses were introduced: a new strain of dengue 2 that caused a major epidemic of dengue hemorrhagic fever in Cuba, and dengue 4, which had never been in the region prior to this. Epidemic activity increased, and has continued into the 1990’s. Dengue 3 is the new virus strain that was introduced in 1993. We think it caused a major epidemic in Nicaragua in 1994 and epidemics in most of Central America and Mexico in 1995. There has been a constant introduction of new viruses into this area, resulting in increased epidemic activity. This slide shows the sequencing of the envelope gene of dengue 3 viruses from all over the world. The viruses from Panama, Nicaragua and Mexico are very closely related to these viruses from Sri Lanka and India that caused major epidemics of dengue hemorrhagic fever in the late 80’s and early 1990’s. We know that this is a newly introduced virus. More recently dengue 3 virus was isolated in the Caribbean for the first time. We expect it to move through the Caribbean and into South America causing a major epidemic. If we view the emergence of dengue hemorrhagic fever in the Americas by decade, we see that there was no disease in the 1970’s; that most of the cases came from epidemics in Cuba and Venezuela in the 1980’s; and in the "90's there are 23 countries which have confirmed dengue hemorrhagic fever that meet the World Health Organization case definition. The disease is now endemic in most of these countries. Dengue in the United States Since 1920 there have been few epidemics of dengue in the US. The last were a small outbreak in Louisiana in 1945 and, more recently, 3 outbreaks in south Texas. The viruses were introduced from Mexico. The vectors for dengue, Aedes aegypti and Aedes albopictus exist in the US and are capable of transmitting epidemic dengue. This scenario, however, seems unlikely since our lifestyle is not conducive to major epidemics of vector-borne disease. Distribution of Dengue in Africa Africa has the poorest dengue surveillance of all of the main geographic regions of the world. Prior to 1980, there were some anecdotal reports, but the only place where viruses were confirmed was Nigeria. From 1981 to the present time, we have seen major epidemics caused by all four serotypes both in West and East Africa. Epidemic dengue hemorrhagic fever has not occurred in Africa as yet. In 1998, dengue has a global distribution in the tropics. Over half of the world’s population, (2.5 billion people), are at risk of dengue infection. We estimate that every year there is probably in excess of 100 million cases of dengue fever. The World Health Organization estimates 500 thousand cases of dengue hemorrhagic fever. The average case fatality rate is about 5%, so 25 to 30 thousand fatalities are caused by dengue hemorrhagic fever each year. Here is the number of countries reporting dengue hemorrhagic fever by decade. The severe form of disease and cases reported to the WHO are expanding dramatically. From 1950 to 1980, not even a million cases were reported. From 1981 to 1995, four times as many cases were reported to the WHO. Economic Impact of Dengue : Puerto Rico We really don’t know what the economic impact of this disease is. It does not have a high fatality rate, but it infects literally tens of millions of people every year. We have a medical economist working for us now in CID in Atlanta. He’s looking at the disability adjusted life years for Puerto Rico from 1984 through 1994. The DALYs lost per million people over this 10 year period of time has gone from 400 up to nearly 1,000. When you compare the DALYs to other major diseases in tropical America, the disability adjusted life years for dengue is of the same order of magnitude in Latin America as malaria, tuberculosis, hepatitis, STDs (excluding AIDS), the childhood cluster (polio, measles, pertussis, etc.), or the tropic cluster (Chagas, shistosomiasis, and filariasis). Dengue, which gets almost no support for prevention and control, has the same order of magnitude as these diseases when you calculate DALYs. Dengue is causing a lot of economic problems and is a major public health problem in much of the tropical world. Aedes albopiclus is an Asian mosquito originally described in Calcutta, India. It was introduced into the United States in the early 1980’s. This shows changing geographic distribution and illustrates the impact that commerce has on emerging infectious diseases Aedes albopictus in 1980, would have essentially had the distribution shown here in red. It is an Asian mosquito that was limited to Asia, and somehow it got out to Hawaii in the Pacific. From 1980 to the present, this mosquito has moved throughout the world. It has infested areas in Europe, )Italy, Albania), Africa, Fiji, United States, the Caribbean, Cuba, Dominican Republic, Mexico, Honduras, El Salvador and Brazil. This mosquito is one of the maintenance hosts for dengue virus in Asia. It is not an efficient epidemic vector, but it is a very ubiquitous arbovirus vector. It transmits a number of viruses including the Encephalidities, Eastern Equine Encephalitis, Lacrosse Encephalitis, and Japanese Encephalitis. We don’t know why it is such a ubiquitous vector. This is the current distribution in the United States. This mosquito puts the human population at higher risk for other arboviral diseases such as Eastern Equine Encephalitis and Lacrosse Encephalitis. It should be of major concern to public health officials in the United States. II. Factors Responsible for Emergence/Resurgence of Vector-borne Diseases Why have we seen such a dramatic resurgence of vector-borne diseases in the past 15 to 20 years? A lot of factors are responsible for this including policy and technical problems. We have seen insecticide resistance develop. More importantly, we have not developed new insecticides to replace the ones that the mosquitoes are resistant to, so we do not have good insecticides anymore. Drug resistance, primarily in malaria, has created problems. Some of the policy decisions to refocus the malaria control program from treating the insects to treating the people had a dramatic impact on the resurgence of malaria in places like India. With the success in the 1950’s, 1960’s and 70’s, the political and economic support were basically withdrawn from a lot of the mosquito-borne disease control programs. All of this contributed to the resurgence. Demographic Changes Probably more important, are demographic changes that have occurred in our society on a global basis. Population growth in the past 50 years since the end of World War II has been phenomenal, and with the uncontrolled population growth has come uncontrolled and unplanned urbanization, especially in tropical developing countries. Cities have just expanded in an unplanned fashion, resulting in a deterioration in the housing, water, sewage and waste management systems. This creates ideal conditions for water borne, mosquito-borne, rodent-borne diseases in these urban areas. This has contributed to the resurgence of infectious diseases in general, but vector-borne diseases in particular. Changes in agricultural practices have also influenced the resurgence or the emergence of vector-borne diseases. Building new dams which flood areas, gives more area for mosquitoes to breed. Some irrigation schemes increase mosquito breeding and population. Clearing forests and moving into previously unoccupied areas puts people in greater contact with potential infectious diseases. This is akin to what has happened in the United States. People have built their houses right out into the wood lot, putting them in close association with Borrelia burgdorferi, the spirochete that causes Lyme disease. Societal Changes Plastics In addition to the demographic changes, there are a lot of societal changes. All of our consumer goods are now packaged in non-biodegradable plastics and cellophane. Because of mismanagement, a lot of these get into the environment, collect water, and make ideal larval habitats for all kinds of mosquitoes. Automobiles We have seen an explosion in the automobile population in the last 20 to 30 years. Every automobile has 4 tires; those tires are used for 3 to 5 years and are discarded. They are non-biodegradable, and they pile up by the millions. They are not only good breeding grounds for mosquitoes, but they are rat harborages. They create a lot of problems. Commerce Our shipping containers provide a vehicle for moving mosquito vectors and vermin around the world. Air Travel We load 747’s and 777’s up with 300 to 400 people and fly them around the world. It provides the ideal mechanism to constantly move pathogens between population centers, especially urban diseases such as dengue. Genetic Changes in Pathogens We do not really have a full understanding of the influence of genetic changes on the pathogens on the emergence of disease. We think that it probably plays a role. There are instances in recent years, such as the Venezuelan Equine Encephalitis epidemic in Colombia and Venezuela in 1995.. There is a lot of opportunity for genetic change in vector-borne disease pathogens because they have to move through two completely different types of hosts: cold-blooded, arthropod hosts, either ticks, mosquitoes or flies, and vertebrate hosts, which are generally warm-blooded. There is selection pressure on these particular agents, especially environmental pressures on both the arthropod and the vertebrate host, so there is a lot of opportunity to select genetic strains of these agents. Deteriorating Public Health Infrastructure Finally, we have seen a deterioration in our public health infrastructure in the past 30 years, decreasing resources, decay in the infrastructure, a shortage of trained personnel, and a total lack of effective vector control for a lot of these diseases. Basically in the past 50 years we have changed our public health approach from preventive medicine to what I call ‘curative medicine.’ This has lead to what I call the "magic bullet syndrome." People do not want to take the responsibility for disease prevention. They prefer to wait until they get sick, and then they expect to be treated and cured. People are not thinking in terms of prevention of these diseases, and a lot of them certainly can be prevented. Climate Change In the popular press, you read all about El Niño and global warming, and how these factors influence changes in vector-borne diseases. Vector-borne diseases, mainly malaria, dengue and yellow fever, are most frequently associated with climate change. We really do not know whether climate change has influenced the emergence of any of these diseases. As far as we can tell, there is no evidence that climate change has been responsible for any of the resurgence or emergence that we have seen to date, but certainly in the future it could be. We’re in the process now of trying to get a National Academy of Sciences, Institute of Medicine committee to study the influence of climate change on infectious diseases with emphasis on vector-borne diseases. In a year or two we may have some better idea. IV. Prospects for the Future What do we do about this? How are we going to reverse this trend? Are we going to just sit back and wait for it to go on, or do we try to reverse the trend of emergent vector-borne diseases? Population Growth and Urbanization Control We have to get a handle on population growth in the world. Most of the population growth in the next 25 years is projected to occur in developing countries, mostly in urban areas. Public health officials do not normally work with waste management officials and city or urban planners. We work in isolation of each other, and we need to get together and start working with the urban planners to gain control of the whole process of urbanization. The place to start is with population control. Emphasize Prevention—Integrated Prevention Programs We need to change the way we think in terms of public health. We have got to stop thinking of epidemic and emergence response and start thinking of disease prevention. A lot of diseases can be prevented. We can develop surveillance systems, have early warning predictive capability, and implement strategies to prevent major epidemics. We simply do not do it because our policy makers are afraid to respond to something unless there is a major epidemic occurring. Politically it is very difficult to get support to prevent a disease, but very easy to get support to respond to an epidemic. We need, public outreach and education. We’ll never be able to do this without the help of the people who are creating the problems that we’re dealing with. We desperately need to rebuild our public health infrastructure, not only in this country but also in countries around the world. In terms of vector-borne diseases, personnel and resources are critical. Of all the major emergent resurgent diseases, infectious diseases, vector-borne really are at the bottom of the pile in terms of economic support and personnel. We need to support research and develop new, integrated prevention strategies including more effective vector control and vaccine research. We need to understand these diseases better to prevent them. Q&A [question: I was just curious about the clinical differences between Lyme disease in Europe and China versus in the United States?] In Europe, Lyme disease has a greater neurologic component, more neurologic disorders associated with it than in the United States where it’s mostly associated with acute arthritis. Some people, however, feel that that distinction is not valid. In the United States a lot of the neurologic disorders associated with Lyme disease are not confirmedIf you have CNS infection, one of the gold standards is to detect antibody in the cerebral spinal fluid. They have been able to do that in Europe at a higher rate than we do the U.S. A lot of people who want to blame Lyme disease for everything. The CDC is trying to support research to try to define what really is Lyme disease infection and what is not. In the southeast and south central part of the United States, where a lot of Lyme-like diseases occur, we have not been able to confirm Borrelia burgdorferi infection. We think that there is a new spirochete that we have detected in that area, and it’s probably associated with another tick vector that is causing some of that disease. [question: There is not a reliable serological test for Lyme diseases.] We do not have a really accurate serologic test yet for Lyme disease, but we do have fairly good tests. A lot of the tests are sensitive, but non-specific. They cross-react with everything. We have worked very hard over the past several years to develop the specificity of the IGM and IGG Western Blot test. Through confirmation by isolation of the spirochete we feel that we have a good two-stage test. In the past, a lot of people developed diagnostic tests using sera that were based on a clinical diagnosis. We have not done that with any other infectious agent to my knowledge. We usually develop tests using sera that have been collected from patients that we know are infected with the agent. We have worked hard over the last 5 or 6 years to isolate borrelia burgdorferi from patients, and use those samples to develop tests. So I would disagree that we do not have a good test. It is not the best test yet, but we do have a reasonably accurate test. AMK: You mentioned the impact of commerce on Aedes albopictus, which presumably was the tire trade. Is that same shipping of microenvironments important to the distribution of Aedes Aegyptus? Are there other solid waste vehicles that you are aware of that are shipped around the world that have created the same kind of transportation for vectors? Aedes aegypti. does not breed in the tire depots to the extent that Aedes albopictus does. Although in the past, tire depots and water barrels on ships were one of the main mechanisms that Aedes aegypti got transported all over the world. Aedes aegypti is primarily an urban species, highly associated with humans, and it prefers to live in urban deserts. Aedes albopictus, although it occurs in cities of the tropics in Asia, is primarily in the larger gardens and does not go inside the houses quite to the extent. If there is a tire pile there, it’ll be almost 100% Aedes albopictus and not Aedes aegypti. If there is a tire laying in the back yard somewhere, then it will probably have Aedes aegypti in it. If you go into the suburban areas where the tire piles generally are, it’ll have Aedes albopictus and not so much Aedes aegypti. It has been responsible for much of the reinfestation of Latin America. AMK: Have you studied new construction sites in the same sense of creating vector microenvironments? Not specifically. We know that that was a major factor in Jedda in 1994, but have not really done any specific sites anywhere else. [question: In the past, the International Health Regulations have only covered three diseases. They are talking about increasing the scope of reportable diseases to include that variety of syndromes including hemorrhagic fevers. Do you think that is going to result in improved international surveillance or distribution of international information about potentially international outbreak, or do you think people still aren’t going to report?] There are two issues here: 1) changing from a disease specific to a syndrome type reporting 2) international cooperation and whether the countries will actually abide by the international health regulations. They have totally ignored it for the last 30 years. I do not know why just by changing to a syndrome reporting system that these countries are going to report more. Some people have reservations about this whole approach and how it is going to work. WHO is becoming much more proactive in changing the international health regulations and enforcing them. [question: How can you maintain a program for a specific disease that is not that important at this time when there are other things that are more pressing? How can you convince people to fund them?] I have felt that the trends in public health in the past 30 years have been unfortunate. Some diseases have not been dealt with the way they should be and, others are totally ignored. We do not enforce things like the International Health Regulations. From a policy point of view, there is no international cooperation and collaboration. Readings: Gubler, D.J. "Epidemic Dengue and Dengue Hemorrhagic Fever: a Global Public Health Problem in the 21st Century". Emerging Infections I, pp. 1-12. Gubler, D.J. "The global resurgence of arboviral diseases". Transactions of the Royal Society of Tropical Medicine and Hygiene, 1996, (90) 449-451. Dennis, David T. "Lyme Disease". Dermatoepidemiology, Vol. 13, Number 3, 1995, pp. 527-547 (optional). Centers for Disease Control.. "Lyme Disease - United States, 1996". Morbidity and Mortality Weekly Report, Vol. 46, Number 23, 1997 (optional). Return to Title Page HOME  |  List of Lectures