Number Of Human Cases Research Articles

Tuberculosis : ¿ una zoonosis re-emergente ?

Tuberculosis is an infectious disease that is found throughout the world and which can have a dramatic impact on the economy and on human and animal health. In humans, the principal cause of infection is Mycobacterium tuberculosis, but the animal-specific pathogen, M. bovis, is arguablythe most important zoonotic agent in human history. Despite the fact that several countries have implemented control programmes for M. bovis infection in animals, which has resulted in a reduction in the number of human cases as well, recent years have witnessed a re-emergence of tuberculosis. This is due to the appearance of strains that are resistant to the main antibiotics used to treat the infection in humans, the spread of the human immunodeficiency virus, the maintenance of wild reservoirs and the persistence of the infection in livestock, particularly in developing regions. Coordinated efforts by human and animal health services, the improvement of diagnostic techniques and the development of more effective vaccines to prevent the infection are the main strategies for controlling this disease.

The rise and fall of Salmonella Enteritidis in the UK.

After rising in the early 1980s, the number of recorded human cases of Salmonella enterica subsp. enterica in the UK has fallen in the last 5 years, with a particular decline in cases of infection with serovar Enteritidis. This decline has been concomitant with the introduction of vaccination of egg-laying hens against serovar Enteritidis. It is likely that other factors such as improved biosecurity in egg-laying flocks, a build-up of immunity in other animals and the rise in the number of livestock infections with host-adapted serovars of Salmonella have also played a part in this decline. Although human Salmonella cases are currently at their lowest level since 1987, it is important to remember that the reasons for the dominance of Enteritidis in human infection are poorly understood and it is possible that other serovars could share similar properties and the eradication of Enteritidis may leave a niche for them to fill.

“Neon Needles” in a Haystack

Passive surveillance is usually viewed as less efficient for case ascertainment than active surveillance. However, for diseases with nonhuman animal reservoirs, active surveillance can be like looking for a needle in a haystack and may be prohibitively expensive. Fortunately for surveillance of West Nile virus (WNV) in the northeast US, the dead crows have served as "neon needles in a haystack"--indicators of viral activity that call attention to themselves. In 2000, laboratory testing of dead birds, including all species, birds found singly, with signs of trauma, or no compatible pathology, provided the first confirmation of viral activity in most areas. The surveillance factor most closely associated with the number of human cases was the dead crow density. In 2001, dead crow densities will be used as an additional index for monitoring human risk and need for prevention and control activities. If there are few crows in an area, if their case-fatality rate is reduced, or if there is public complacency about reporting dead crow sightings, this passive surveillance indicator may not be helpful in identifying areas likely to have occasional human cases or an outbreak.

Seasonal variation in prevalence of antibody to hantaviruses in rodents from southern Argentina.

We conducted a small mammal trapping study to investigate temporal variation in prevalence of infection in hantavirus reservoir populations in the Patagonian Andes mountain range, Rio Negro province, Argentina. Rodent blood samples collected in natural and periurban habitats and at the home of an hantavirus pulmonary syndrome (HPS) case patient were analysed by enzyme-linked immunosorbent assay. Organ tissue samples were tested by polymerase chain reaction (PCR) and nucleotide sequence analysis. Eight species of 1032 rodents were captured in 15 551 trap nights, giving an overall trap success of 6.6%. Hantavirus antibody was detected in 30 of 555 Oligoryzomys longicaudatus (reservoir of Andes virus), three of 411 Abrothrix longipilis, and one of 10 Loxodontomys micropus. Antibody prevalences in O. longicaudatus were 13.7% in spring 1996, 59.3% in summer 1996, 2.1% in autumn 1997, 12.4% in winter 1997 and 3.1% in spring 1997. A much higher antibody prevalence (33%) was found during trapping around the residence of an HPS case patient. Higher prevalences were found in older male O. longicaudatus. There was no apparent correlation of antibody prevalence with rodent population density, or of rodent population density or antibody prevalence with numbers of human cases. For an HPS case that occurred in our study area in 1997, we identified the probable rodent reservoir and likely site of exposure by matching the genetic sequences of virus obtained from a rodent and the HPS case patient.

Estimating the economic effects of cystic echinococcosis. Part 3: Jordan, a developing country with lower-middle income.

The economic costs of cystic echinococcosis (CE) in Jordan, a developing country of lower-middle income, were investigated. Initial cost-estimates for livestock were based on the published prevalences of Echinococcus granulosus infection in sheep and goats and the values of livestock-related products together with likely production losses. Likewise, the annual numbers of human cases of CE were estimated using published surgical incidences in man. The costs of surgery were estimated from hospital records and by costing out the procedures each patient received whilst undergoing treatment. After comparing the quality of life of patients treated for CE with that of case-matched controls, it appeared that the treated patients had some long-term morbidity caused either by the disease or the resulting treatment. A simple spreadsheet model was built up, to sum the individual cost items. Each cost item and each of the data related to prevalence and incidence was assigned a mathematical distribution and varied randomly, using Monte-Carlo techniques, throughout its range, over 10 000 simulations. The results of the study indicate that the most likely range of annual economic losses attributable to CE in Jordan (encompassing 95% confidence limits) is from U.S.$2 602 215-6533 661, with a median of U.S.$3 874 070.

Health risks of travelers in South Africa.

Large numbers of tourists visit South Africa every year. Travelers to urban areas are at little risk of contracting an infectious disease, however the adventure traveler is at increased risk. Yellow fever is not known to occur in South Africa. Malaria is endemic in Mpumalanga and KwaZula-Natal. Schistosomiasis is endemic in large parts of the country. Although rabies is found throughout the country, only a small number of human cases is reported. High risk areas are KwaZulu-Natal, the eastern Cape and Mpumalanga provinces. The incidence of human immunodeficiency virus (HIV) infection is high and counseling regarding sexually transmitted diseases is important. Sanitation of water is excellent in most large cities and towns; however travelers to rural areas should exercise caution. Arbovirus infections do occur but relatively few cases are reported. The hiker is at risk for tick bite fever and should be counseled. Since the abolition of apartheid, South Africa has been seen as an inexpensive, high quality destination by many tourists. In 1997, a total of 5,436,848 travelers from many different countries visited the country. Areas most frequently visited include Johannesburg, Cape Town, Durban, the Garden Route, Kruger National Park, KwaZulu-Natal and Pretoria. The most common reason for visiting the country was holiday (44%), followed by visiting friends and relatives (23%), business travel (27%) other (6%).1 Travelers, to the larger cities such as Johannesburg, Cape Town and Durban are at little risk of acquiring an infectious disease. The adventure traveler however is at greater risk as parts of the country are endemic for malaria, schistosomiasis, rabies, food and waterborne diseases, sexually transmitted diseases and arbovirus infections. Accidental deaths due to motor vehicle accidents and interpersonal violence are important health risks in South Africa. Travelers visiting popular attractions are at significantly lower risk. However this has never been quantified. This review aims to address the occurrence of infectious diseases and attempts to give guidelines to practitioners caring for travelers.

Studies on control of visceral leishmaniasis: impact of dog control on canine and human visceral leishmaniasis in Jacobina, Bahia, Brazil.

To assess the effect of removing leishmania-infected dogs on the incidence of visceral leishmaniasis, a controlled intervention study was performed in northeast Brazil. The attempted elimination of seropositive dogs resulted in an initial significant decrease in the annual incidence of seroconversion among dogs from 36% to 6% over the first two years. In the following two years, the incidence increased to 11% and 14%, respectively. In a control area in which dogs were surveyed but seropositive dogs were not removed, the cumulative incidence did not vary significantly from year to year, ranging from 16% to 27%. In the intervention area, the prevalence of dog seropositivity decreased from 36% before the intervention to 10% and remained stable. These findings suggest that attempting to remove seropositive dogs is insufficient as a measure for eradicating visceral leishmaniasis in dogs. However, the force of transmission of infection among dogs can be reduced by such programs. Also, when the number of human cases before and after the start of the intervention was calculated, a significant decrease in incidence of disease in the intervention area was observed among children less than 15 years of age (P < 0.01). The results of this intervention study suggest that the elimination of the majority of seropositive dogs may affect the cumulative incidence of seroconversion in dogs temporarily and may also diminish the incidence of human cases of visceral leishmaniasis.

Arthropod Research in the Southeastern U.S.

A short description of the Institute of Arthropodology and Parasitology (IAP) at Georgia Southern University is presented. The largest and best tick collection in the world is located there as is one of the leading tick research programs. Additionally, the Institute conducts excellent non-tick related programs. The IAP provides consulting service and tick identifications to the public and to agromedical specialists. A major research effort involves Lyme disease and its tick vectors in the southeastern U.S. Lyme disease accounted for more than 90% of all arthropod transmitted diseases in the U.S. during 1992 (9,895 cases). Misinformation about Lyme disease is noted and some exciting research breakthroughs on this disease in the southeastern U.S. are reported. Clearly, the Lyme disease pathogen, Borrelia burgdorferi, is cycling enzootically in the South. Because of misinformation and poor surveillance, the number of human cases in the South is unknown.

Computer Simulation of Management Strategies for American Dog Ticks (Acari: Ixodidae) and Rocky Mountain Spotted Fever

Computer models were developed to simulate the effects of management technologies on populations of the American dog tick, Dermacentor variabilis (Say), principal vector of Rocky Mountain spotted fever (RMSF) in eastern North America. The technologies modeled were area-wide acaricide application, acaricide-food-baited tubes for self-treatment by small mammals, dipping of dogs in acaricides, acaricide-impregnated plastic dog collars, reduction of small mammal host populations (host management), and removal of vegetation that protects free-living tick stages (vegetative management). Submodels for each of these technologies were incorporated into a model (ADTSIM) for the population dynamics of the tick and RMSF transmission. Comparisons of simulated and observed data were used to verify reasonable accuracy of the submodels. Repetitive simulations were made to identify levels and timing of each control method (alone or combined) required to reduce tick populations below a RMSF transmission threshold of 252 unfed adults/ha. Eight to 30 acaricide applications, depending on acaricide and percentage of population treated, were needed during a 10-yr period to reduce densities of ticks below the threshold. The baited-tube method, host management, and vegetative management (depending on level and frequency of treatment) also were capable of reducing tick density below the threshold. However, acaricide-impregnated plastic dog collars did not reduce tick density below the threshold unless at least 50% of the hosts of adult ticks were domestic dogs. Integrated strategies were developed for management of ticks and RMSF in six selected states. These strategies reduced numbers of human cases of RMSF 90% or more by year 20 by maintaining tick densities between 100 and 252 unfed adults/ha.

Cryptosporidiosis: Clinical Features and Diagnosis

Cryptosporidiosis is an infectious disease caused by the coccidian parasite Cryptosporidium spp. that primarily infects the gastrointestinal tract of animals. Prior to late 1982, only 11 cases of human infection had been reported, with the first human case reported in 1976. During the 1980s, the number of human cases began to rise dramatically. Most of these patients were immunodeficient, many of whom had the acquired immune deficiency syndrome (AIDS). Immunocompetent individuals can also acquire the infection with mild-to-severe diarrhea lasting from several days to weeks. Immunocompromised patients develop severe, irreversible diarrhea, often thought to be a significant contributing factor leading to death. Although many therapeutic compounds have been tried, none have proven to be very successful. The incidence of this infection is worldwide, with many published reports of infection in both immunodeficient and immunocompetent individuals. The diagnostic approach has been expanded to include stool examinations using modified acid fast procedures and fluorescent monoclonal antibody reagents. Although histological methods are still routinely used for biopsy specimens, the examination of stool has proven to be a very effective, noninvasive procedure. In addition to the gastrointestinal tract, other areas of the body that have been found to be infected with this organism include the respiratory tract and the biliary tree and gall bladder epithelium. Screening for this organism may become very important in known risk groups (animal handlers; children, staff members, and contacts of those who attend day care centers; travelers; and those who are immunodeficient), particularly if an effective therapy is found. Some laboratories screen every specimen submitted for an ova and parasite examination, while others have limited their testing to specific requests, risk groups, and those patients who are symptomatic.

Benefit-cost analysis of bubonic plague surveillance and control at two campgrounds in California, USA.

A benefit-cost analysis was performed at the request of the California Department of Health Services on its plague control program at 2 California campgrounds. In addition to the current control program, consisting of surveillance and control, a surveillance-only program and 2 no-program alternatives were considered. The results showed that the current control program was economically preferable, with an average annual net benefit of ca. 2000. Ranking the suboptimal alternatives showed that the no-program/open-park alternative was the next preferable, followed by the surveillance-only program, then the no-program/park-closure alternative. Sensitivity analysis showed that the current control program would remain optimal if the initial assumptions were reasonably accurate. However, the results were highly sensitive to the assumed number of human cases and frequency of epidemics. Slight overstatement of these factors might incorrectly favor the current control program over the no-program/open-park alternative. Methodology developed in this study may be applied to an evaluation of the California (or other statewide/regional) plague control programs.

Anisakiasis From the American Perspective

Human anisakiasis results from accidental infection with larval ascarid nematodes, which normally parasitize several phyla of marine life during their complex life cycle.1,2Larvae from two genera,Anisakis and Phocanema, of the family Anisakidae, have been definitely identified from human cases, butAnisakishas produced by far the greater number of human cases. Adult worms of these two genera infest the stomachs of marine mammals, attaching and burrowing into the mucosal surface in dense clusters. Unembryonated eggs passed in the stool develop and hatch in sea water to produce sheathed secondstage larvae. After ingestion by a small crustacean, the larva molts and encysts in the crustacean's body cavity. The larval worm then encysts in the viscera or muscles of any fish that eats these parasitized crustaceans. Fish or squid that eat other parasitized fish also become parasitized. During repeated passages from one fish to another, the larvae may grow

Ductular origin of pancreatic cancer and its multiplicity in man comparable to experimentally induced tumors. A preliminary study

The histologic features of 3 randomly selected pancreatic cancer cases are compared with those found in Syrian hamsters after treatment with N-nitrosobis(2-oxopropyl)amine (BOP). The 3 human cases all exhibited hyperplastic, preneoplastic and malignant changes which were markedly multicentric, and which arose predominantly from ductules, as well as from small ducts. The findings were comparable to those in the hamster mode. Proliferation and malignant alterations of the intrainsular ductules were commonly seen in both human and experimental tumors. The data is consistent with the concept that cells of the small ducts and especially of the ductules represent a potential source of human, as well as experimental, tumors. The small number of human cases studied does not allow generalization, but the marked resemblances in all 3 randomly selected pancreatic cancer cases were remarkable.

Experimental animal model for encephalitis due to herpes simplex virus.

Investigations of the pathophysiology and therapy of encephalitis due to herpes simplex virus have been hampered by the lack of appropriate experimental animal models, the relatively small number of human cases, and the variable spectrum of clinical disease. An animal model was developed in the adult hooded rat for encephalitis caused by type I herpes simplex virus; the disease is reproducible, restricted to the brain, and has histopathologic features similar to those produced by the disease in humans. Two hundred twenty-two animals, including appropriate controls, were studied. The model provides a clear mortality endpoint with reproducible results and an inoculum-dependent response. Infection is characterized by a twoto four-day period of incubation followed by signs of infection of the central nervous system; the average survival time of infected rats is seven days.

Spontaneous Histoplasmosis Occurring in a Dog 1

Summary and Conclusions 1. The third instance of a generalized infection in a dog by Histoplasma capsulatum is reported. 2. Material was not available for the cultivation or passage to other animals, but the morphologic characteristics and the reactions of the host are identical with previously described cases of this disease. 3. The importance of the occurrence of the disease in an animal pet in an area in which a number of human cases have been reported is stressed. 4. The possibility of the various methods of transmission from dog to man as postulated by De Monbreun is discussed. 5. The majority of evidence suggests either the respiratory or the gastro-intestinal tracts as the portal of entry.

HEMOCHROMATOSIS

Hemochromatosis is a chronic disease characterized by the presence of large quantities of hemofuscin and hemosiderin in the tissues, particularly in the liver and pancreas. The iron in this pigment is apparently of both endogenous and exogenous origin. The exact mechanism of this dysfunction of iron metabolism is, as yet, not known. Mallory 1 has produced a pigment cirrhosis of the liver in animals by means of the prolonged administration of copper salts and also finely divided metallic copper. In a large number of human cases there has been a history of chronic copper poisoning either through occupational contact or through the prolonged ingestion of beverages or foods containing copper. The following case has been under observation for almost six years, during which time some interesting features have been observed, particularly those associated with the diabetic manifestations: REPORT OF CASE A white man, aged 42, single, a cabinet maker, admitted

The Relation of Rat-fleas to Plague in Shanghai

1. Though Shanghai is in close communication with ports in which plague is endemic, it has not suffered severely.2. The number of human cases is small compared with the number of plague-infected rats found.3. Both X. cheopis and C. fasciatus are found. Reasons are given for considering that X. cheopis is the chief agent in spreading plague, and that infection, being unlikely to reach Shanghai during the season when this flea flourishes, has difficulty in gaining a foothold.4. The discrepancy between the number of cases of human and rat plague may possibly be explained by the habits of C. fasciatus.