Lyme Borreliosis Known As Lyme Disease Biology Essay


Lyme Borreliosis, known as Lyme disease, is an infectious disease first identified in 1975, in a cluster of supposed arthritis cases in children in the towns of Old Lyme and Lyme, Connecticut. Initially called Lyme arthritis, it was determined that the juvenile arthritis was a late stage manifestation of the disease. It was recognized to be a tick-borne disease in 1981, after the bacterial spirochete Borrelia burgdorferi, the etiologic agent, was recognized in Ixodes scapularis. It is a multisystem disease that is prevalent in North America, Europe, and Asia. It results from the infection of four microaerophillic spirochetes of the family Spirochaetaceae, and all four of the species belong to the Borelia burgdorferi sensu complex. Those species of bacteria are B. burgdorferi sensu stricto , B. afzelii and B. garinii and B. japonica. In the United States, it is mainly caused by Borrelia burgudorferi sensu stricto and is classified as a biosafety level 2 disease.

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The spirochete is transmitted to humans by an infected tick bite. Transmission in the U.S. to humans is predominantly by infected Ixodes scapularis dammini and I. pacificus ticks, though it can also be spread by I. ricinis. Allen Steere, recognized it as a vector-borne disease however it was only in 1981 that Willy Burgdorfer determined the exact tick B. burgdorferi sensu stricto. In reservoir hosts; inclusive of squirrels, shrews, mice and other small invertebrates, B. burgdorferi is present naturally. Ixodes scapularis and Ixodes pacificus (black legged or deer ticks), while blood feeding on these reservoir hosts, become infected. It is during subsequent blood meals that the ticks are able to transmit the infection of the disease, among reservoir hosts or to incidental hosts which include humans. Deer are not infected with B. burgdorferi, but they are able to transport ticks and thus help to maintain tick populations. B. burgodoferi is most frequently linked to ticks hosted by white-tailed deer and white -footed mice most often and B. afzelli most associated with rodent-feeding vector ticks. Both B. garinii and B. japonica are also linked to birds. In California, there was some controversy regarding how B. burgdorferi sensu lato was able to remain in an enzootic cycle, since there was a huge lizard population, and this was at first thought to reduce the number of B. burgdoferi in tick populations however, it is now under investigation since lizards can be infected but cannot infect the ticks that feed upon them; if infected. Studies have shown that lizards have a very species specific relation to the enzootic cycle, and thereby exist in some refractory relation to infection with B. burgdorferi sensu complex. Ixodes ticks are found at ground level where the relative humidity is high, in temperate climates. In the Eastern states of the U.S. , they are found in leaf litter habitats such as deciduous forests. In North Central, I. scapularis is usually found in highly wooded regions surrounded by cleared land for agriculture. On the Pacific side, I. pacificus is found in many areas such as forest, scrub and grasslands.

The disease progresses with cutaneous manifestations in both premature and later stages, The infected person shows symptoms in early stages of a skin rash; Erythema Migrans (EM) which is circular and characteristic of the disease, other symptoms include fatigue, headache, fever and depression, chills, muscle and joint aches, and swollen lymph nodes.  In some cases, these may be the only symptoms of infection. It is easily treated with a course of antibiotics spanning some weeks, but if it is untreated, symptoms worsen and are harder to treat later on. Lyme disease can infect many different parts of the body and thus cause numerous symptoms at different times. Some of the symptoms of Lyme disease are actually synonymous with symptoms of other diseases. The symptom that appears first is the rash, this symptom will appear in almost 70-80% of those infected with the disease, it is at the point of infection ie. the actual bite. The appearance is delayed and occurs from 3 to as much as 30 days after the bite. After it first appears, it grows in size to almost 12 inches after a number of days, appearing almost as a bull's eye since the center may clear. This rash is usually warm to the touch and many patients actually also develop other EM rashes on other parts of the body as well. If it is not treated, the symptoms worsen as the infection spreads; sometimes it is possible that all of these symptoms will sometimes end even without treatment. After some months almost 60% of all patients with untreated conditions will develop severe symptoms of joint pain, swelling and arthritis which maybe intermittent, the targeted area is usually the knees. Untreated patients, almost in 5% of cases, end up with chronic conditions involving neurological difficulties years after having been infected. These chronic conditions involve short term memory, concentration difficulties, numbing of both hands and feet and shooting pains. While most are cured with antibiotics, with early treatment in the majority of the cases, there are some patients whose symptoms still last months to even years after treatment. Untreated infections after months to years can result in peripheral neuropathy, encephalopathy or mono- or oligoarticular arthritis. This involves joint pains, muscle pains, arthritis, cognitive defects, sleep difficulties, and tiredness. While the reason for these long term symptoms is not certain, it is thought that it is an autoimmune response that allows for the immune system to continue with a response after the infection is gone.

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Diagnosis is based on symptoms exhibited by the patient, including the EM rash. Prognosis also involves determining whether the patient had been previously exposed to ticks and diagnostic laboratory testing. Diagnosis is based on clinical manifestations of symptoms of the infection and also possible exposure to ticks that have been infected. Those who show the characteristic EM rash with an onset time of two to three weeks do not need a diagnostic test. Patients who show cardiac, neurological or musculo-skeletal symptoms can confirm diagnosis with the recommended two-tiered serological testing. Other methods are not strictly recommended. Treatment is with antimicrobials and those demonstrating EM are usually treated with oral doxycycline, amoxicillin, or cefuroxime axetil. Other patients are given oral or intravenous antimicrobials depending on their manifestation. B . burgdorferi is not a communicable disease and no infections have been shown after transfusion or contact with blood or urine of an infected person.

Lyme disease is one of the fastest growing infectious diseases, and the most commonly reported vector-borne illness in the United States and is the most common tick borne disease. The average ratio of reported cases is 7.9 cases for every 100,000 persons. In the 10 endemic states the ratio was 31.6 cases for every 100,000 persons for the year 2005. Most of the cases are in the areas of West-North Central, East North Central, South Atlantic, Mid-Atlantic and New England. The Center for Disease Control (CDC) in 2008, defines confirmed surveillance of Lyme disease cases through three major laboratory ways and gives equal weight to each: the first being a positive culture for bacterium burgdorferi, the second being two-tier testing through confirmation by ELISA screening and Western Blot; and a single tier IgG Western blot (that shows the presence of an old infection). Before 2008, the only way the CDC had surveillance cases was through the positive culture and two tier testing; now it allows for Western Blot without any ELISA screening having taken place. Lyme disease is reported to the Centers for Disease Control and Prevention, under the umbrella of the National Notifiable Disease Surveillance Systems. From the period of 1992 to 2006, there 248,074 cases of Lyme disease reported in the U.S.. There was a yearly increase in the cases, by 101%, from 9,908 cases in 1992 to 2006 having 19,931 reported cases. Of all the cases, incidence was highest among 10 states which accounted for 93% of cases during this 15 year period. The majority of cases occur in the northeastern and north-central states. The states with the highest prevalence were Connecticut, Delaware, Massachusetts, Maryland, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island, and Wisconsin, these were also targeted by the Healthy People 2010 initiative, referred to as the HP 2010 states. Surveillance of the disease by CDC began in 1980, however before 1991 case definitions and reporting practices were varied among states hereafter the Council of State and Territorial Epidemiologists (CSTE) recognized Lyme disease as a Nationally Notifiable Disease. 248,074 Lyme disease cases have been reported during 1992 to 2006, there has been a steady increase during the 15 year period of 101% from 9,908 to 19,931 cases in 2006. The state mean ranged from <0.01 cases per 100,000 population in Montana and Colorado to 73.6 cases per 100,000 population in Connecticut. The 10 states with the most endemic Lyme disease showed 229,782 cases thus representing 92.6% of overall cases and per single year 88% of cases. Of the 10 annual rates, Connecticut, Delaware, and Rhode Island were more variable due to changes in surveillance. Per County rates, the mean reporting the minimum of one case was 714 the number in a range of 625 to 796. The percentage of counties having more than one case, exceeded 75% in the six states of Connecticut, Delaware, Massachusetts, Maryland, New Jersey, and Rhode Island through the entire 15 year period. The disease disproportionately affects the population, most frequently infected are children; aged 5 to 14 years, and males, since 53% of all reported cases occurred among them. Per demographics, there were peaks in the rates of average annual infection among children aged 5 to 9 approximately 8.6 cases per 100,000 population. There were also high trends in adults, 55 to 59 years around 7.8 cases per 100,000 people. For men for there was a rate of 6.3 for men compared to women at 5.4 at a yearly rate. This was most in effect for those of the age 5 to 19, as there was an increase of 194% percent compared to 114% in females of the same age group comparing 10.3 to 6.2 cases in 2006 per 100,000 persons. In terms of race, 94.1 % of reported cases were white and 1.7% were black. For the 10 HP 2010 states the modal age was 7 and males made up 53.4% of the cases whereas in the other states the most frequent age was 44 and males made up 49.4 % of the infected. Of all the cases, EM was seen in 69.2%, arthritis along with joint swelling in 32%, neurological symptoms in 12% and some degree of atrioventricular block for .8% of the cases. Of all the cases, there were more than one clinical symptom in 12.8% of the cases. The symptoms were varied among the younger age groups and as well in the HP21010 states. In younger ages those less than 20, there have been high rates of arthritis 38.7%, and low rates of EM 58.2% for children 10 to 14 years. Infection peaks in cases of children, males and whites. It is not known why it there is a disparity in young males and young females. The popular demographics can be used for a prevention campaign for those more likely to become infected.

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Seasonality has been exhibited, as 65% of patients with EM had illness onset in June and July. Lyme disease is not limited by month however some seasonality has been identified. Most persons had onset of the disease in the months of June-25.7%, July-30% and August 12.1 %. These are the three months in which ticks seek actively mammalian hosts and also the months in which human outdoor activity is the most popular. In showing of clinical symptoms, 67% of patients with EM had their onset in the months of June and July, but those with arthritis comprised only 37%.

Prevention of Lyme disease includes using insect repellent outdoors, landscaping around homes, removing ticks and external pest control. Ticks that transmit Lyme disease may also carry other diseases. The CDC recommends to prevent Lyme disease, individuals must avoid tick infested areas, use insect repellant on exposed clothing and skin containing 20-30% DEET (N,N-diethyl-m-toluamide) and perform tick self-examinations on a daily basis. Around private residences and recreational areas, tick populations can be lessened by excluding deer, removing leaf litter and bush litter and making a buffer zone of possibly materials such as gravel or wood chippings between lawns and forests and also by applying acaricides. The disease can be lessened by immediate and appropriate tick removal and seeking medical help for treatment of early symptoms. For those persons bitten with an attached tick of either I. scapularis or I. pacificus for more than thirty six hours, a single dose of doxycycline should be considered for prophylaxis of Lyme disease within 72 hours after tick removal. Protective footwear is advised, as well as light colored clothing so that ticks can be easily seen. In Eastern US homes there have been studies that have shown a 72-100% decrease in tick population, after leaf litter has been taken away and the habitat modified.

In 1999, a vaccine was licensed for us however this was pulled due to limited efficacy in 2002 by the manufacturer. Prior infection does not prevent another infection and repeated infections have been found. The disease being fatal is rare and also very unlikely is the severe chronic form of the disease.

The increase in Lyme disease can be attributed to many factors, and it still remains intense in the north central and north eastern states. The reasoning behind this wave of increases is that there have been better surveillance, more awareness of the disease by both public and health workers, possible misdiagnosis as well as errors in reporting but also a real and true increase in the number of cases. In 6 of the HP 2010 reference states the regularly reported cases increase may have been due to an increase in tick densities and also furthering of human development in suburban and rural areas; this refers to the states of Maryland, New Jersey, Rhode Island, Connecticut, Delaware and Massachusetts. For the other HP 2010 reference states, the considerable increase especially in the states of Wisconsin, Pennsylvania and Minnesota has been linked to the expansion geographically of vector ticks and reservoir mammals into areas that are new. In states of the Southeast, the surveillance of the disease can be further be confused with tick associated rash sickness present in the south that closes resembles the initial stages of Lyme Disease, the cause of this is not B. burgdorferi.

Healthy People is a national initiative to set 10 year objectives for the health of all Americans. The Healthy People 2010 target for the 10 states with endemic states was suggested from the baseline of 17.4 cases per 100,000. However, in the 3 year period between 2003 to 2005 the average annual rates in the 10 states were 29.2 cases per 100,000. This goal was targeted with intention that the vaccine, first licensed in 1999 would be used across the board. However since the vaccine was removed the situation remains that persons are now only educated about prevention of infection, and how to reduce tick populations outside of homes and other types of recreational areas. Studies show that educational campaigns have made an increase in awareness, yet persons still fail to tuck their pants into their socks , landscaping homes and avoiding forests. Those already infected have been informed to receive prompt diagnosis and treatment. Universities, health departments, government agencies and private sectors continue to work to lessen the risk factors of and the ecology of Lyme disease more specifically in the endemic states as part of an overall trend to utilizing space technology to prevent human disease. There is hope that this will lead to early warnings as well as identification of hot spots. The Public health situation shows that there have been benefits to the disease surveillance and there is still room for improvement. However Public health workers can now be able to define the distribution and trends of the disease. Local health departments however have been burdened as the cases numbers increase and electronic lab reporting has been implemented, causing some departments to modify their surveillance causing a variance in case tallies. This was why the Lyme disease definition was restructured in 2007 in order for more manifestations of the disease to be reported as well as making it easier for cases to be reported, thus requiring more lab evidence and also allowing for also probable cases to be reported. There are limitations on the data, being that it is not known how much off all cases are actually reported, in endemic areas cases are more likely to be underreported and over reported in other areas. Over reporting and certain misdiagnosis can account for some of the demographic differences in HP 2010 endemic states and the other states, reporting practices also vary by state due to available reporting resources for Lyme disease surveillance. Reported cases are based on the patient's residence and not where the infection occurred and cannot be seen as transmission locally.

The number of cases continues to increase showcasing the need for more prevention campaigns and strategies, early treatment and diagnosis, and a sustained surveillance reporting system. Infections increased disproportionally in children especially males. Geographic expansion was noted in the states of Wisconsin, Pennsylvania and Minnesota. The cases in HP 2010 states had different features compared to the other states and this may be suggesting incorrect reporting or certain differences in the epidemiology of the disease in non-endemic areas. Intensive surveillance methods should be included in this to better grasp an understanding of the disease such surveillance for vectors and dog serological testing. As Lyme disease continues to emerge rapidly, there is greater need for more prevention campaigns, surveillance and research.