Total Prevalence Of Infection Research Articles

Prevalence of Calodium hepaticum (SYN. Capillaria hepatica) in Rattus norvegicus in the urban area of Rio de Janeiro, Brazil.

The nematode Calodium hepaticum (syn. Capillaria hepatica) is a zoonotic helminth found mainly infecting rats. It was studied the prevalence of C. hepaticum infection in Rattus norvegicus in an urban area of Rio de Janeiro (Brazil), with low urban planning and sanitation. The presence of C. hepaticum was identified through visible yellowish-white lesions in liver tissue and histological analyses. The total prevalence of infection was 45%, with no significant differences between sex and age. The presence of infected rodents near the peridomestic area poses substantial risk to human health.

MOLECULAR SURVEY OF CANINE MICROFILARIAE SPECIES IN EAST-AZERBAIJAN PROVINCE OF IRAN

Filariasis in dogs is caused by several species of filariids. Because of importance of this infection in veterinary medicine and public health, it is necessary to carry out an epidemiological and cross sectional studies in various geographical areas and use of well-adapted diagnosis methods. In this study 205 capillary and whole blood samples were collected from doges in various counties of East-Azerbaijan province. Samples after preparation were examined by Knott`s test and light microscope for presence of microfiler. In molecular identification, Pan-filarial and species-specific PCR perimers was used to differentiate among Dirofilaria immitis, Dirofilaria repens, Acanthocheilonema reconditum, Acanthocheilonema dracunculoides, Brugia malayi and Brugia pahangi. Descriptive statistics were used for data analysis. Total infection prevalence with the microscopic evaluation was 77 (37.5 %) and in PCR test was 94 (45.8 %). The most common species of canine filarial parasite identified in this study was D. immitis 54 (57.4 %) followed by Acanthocheilonema species 40 (42.6 %). The molecular evidence on the sequence of the ITS-2 region provided strong evidence that the canine microfilariae discovered in this study belong to a novel species of Acanthocheilonema. Information about infection prevalence helps us to improve disease management practices in the studied area, apply new hygiene policy and reduce extra costs of therapeutic agents and PCR is a quick and accurate molecular genetics method for detection of filarial species.

Geographical distribution and prevalence of Borrelia burgdorferi genospecies in questing Ixodes ricinus from Romania: A countrywide study

The paper reports the prevalence and geographical distribution of Borrelia burgdorferi sensu lato (s.l.) and its genospecies in 12,221 questing Ixodes ricinus ticks collected at 183 locations from all the 41 counties of Romania. The unfed ticks were examined for the presence of B. burgdorferi s.l. by PCR targeting the intergenic spacer 5S–23S. Reverse line blot hybridization (RLB) and restriction fragment length polymorphism (RFLP) analysis were performed for identification of B. burgdorferi genospecies. The overall prevalence of infection was 1.4%, with an average local prevalence between 0.75% and 18.8%. B. burgdorferi s.l. was found in ticks of 55 of the 183 localities. The overall prevalence B. burgdorferi s.l. in ticks in the infected localities was 3.8%. The total infection prevalence was higher in female ticks than in other developmental stages. Three Borrelia genospecies were detected. The most widely distributed genospecies was B. afzelii, followed by B. garinii and B. burgdorferi sensu stricto (s.s.). The study is the first countrywide study and the first report of B. burgdorferi s.s. in Romania. The distribution maps show that higher prevalences were recorded in hilly areas, but Lyme borreliosis spirochetes were also present in forested lowlands, albeit with a lower prevalence.

Comparison of helminth infection between the sexes of Clarias batrachus (LINN.) from Rupandehi, Nepal

One hundred and twenty specimens of catfish Clarias batrachus were examined for parasites. They comprise sixty specimens each of males and females. 25(41.67%) males and 25(41.67%) females showed parasitic infection. A total of seventy six intestinal helminthes belonging to three taxonomic groups were recovered. They are cestodes – Lytocestus indicus, Pseudocaryophyllaeus clariae; nematodes – Paracamallanus sp., Procamallanus cancilus and acanthocephalan – Acanthocentis sp. Of these, twenty nine were recovered from males and forty seven from females. Total prevalence of infection was the same for both sexes but total intensity of infection was different. There was no statically significant difference in the infection between the two sexes.DOI: http://dx.doi.org/10.3126/ijasbt.v1i2.8197 Int J Appl Sci Biotechnol, Vol. 1(2): 72-74

MOLECULAR IDENTIFICATION OF NOSEMA SPECIES IN EAST- AZERBAIJAN PROVINCE, IRAN

Nosema is a genus of microsporidia, which have significant negative impacts on honeybees. The aim of this study is the epidemiological evaluation and molecular characterization of Nosema spices in various counties of East-Azerbaijan province (Northwest of Iran). 387 samples were collected from colonies maintained in various counties of East-Azerbaijan province. Samples after preparation were examined by a light microscope for presence of Nosema spores. PCR method (SSUrRNA gene) was used to differentiate between Nosema apis (N. apis) and N. ceranae. Descriptive statistics were used for data analysis. Total infection prevalence of the microscopic evaluation and PCR tests were 225 (58.1%) and 260 (67.1%) respectively, total validity of PCR test against the microscopic test was computed equal to 1.1 in this case. Disease distribution in various counties of study area was variable and N. ceranae was the only Nosema species found to infect honeybees. The one species presence and different distribution of Nosema positive samples in various counties of East-Azerbaijan province may be due to multiple reasons. Furthermore, epidemiological information helps us to improve disease management practices in the studied area, apply new hygiene policy and reduce extra costs of production.

Acanthocephalans in northern fur seals (Callorhinus ursinus) and a harbor seal (Phoca vitulina) on St. Paul Island, Alaska: species, prevalence, and biodiversity in four fur seal subpopulations

Monitoring studies of acanthocephalans in northern fur seals (Callorhinus ursinus Linnaeus, 1758) (NFSs) and a harbor seal (Phoca vitulina Linnaeus, 1758) were performed on St. Paul Island, Alaska, in July-August 2011. Gastrointestinal tracts of 105 humanely harvested NFS subadult males (SAMs) (3-4 years old) were collected during the annual Aleut subsistence harvest at four haul-out areas (HOAS): Lukanin (n = 26 NFSs), Polovina (n = 28), Gorbatch (n = 30), and Morzhovyi (n = 21). One gastrointestinal tract collected from a harbor seal (about 3-4 years old) found dead at Morzhovyi HOAS was also examined. The total prevalence of infection in NFSs with acanthocephalans was 29.52 % with variations from 7.69 % to 47.62 % between the four different HOAS. Eight acanthocephalan species of two genera-Corynosoma Lühe, 1904 (Corynosoma strumosum, Corynosoma alaskensis, Corynosoma cameroni, Corynosoma semerme, Corynosoma similis, Corynosoma validum, and Corynosoma villosum), and Bolbosoma Porta, 1908 (Bolbosoma nipponicum)-were found in the NFSs and a harbor seal. This is a new record of C. alaskensis for the NFSs. Short biological notes of the species found are presented. Differences in species composition as well as in prevalence of acanthocephalans parasitizing NFSs were observed in subpopulations from four different HOAS on St. Paul Island. The highest biodiversity of acanthocephalans and infection were found in subpopulations on Polovina and Morzhovyj HOAS, the lowest was on Lukanin HOAS. From 3.2 % (for C. validum) to 19.4 % (for C. villosum) of NFSs were infected by one acanthocephalan species; two species were found in 22.6 %; three in 9.7 %; and four in 3.2 %. Further studies of NFS parasites are necessary to follow the trends in parasitic infection rates and diversity in NFS population on the Pribilov Islands and for monitoring the influence of various ecological factors on NFS populations in Alaska.

Prevalence of intestinal parasites in private-household cats in Japan.

The present study is the first national investigation of intestinal parasites in private-household cats in Japan. A total of 942 faecal samples were collected from private-household cats. Giardia species was assessed using an enzyme-linked immunosorbent assay kit and other intestinal parasites were identified microscopically. The overall prevalence of intestinal parasites was 10.1%; two protozoan parasites (Giardia species and Cystoisospora species) and five helminths (Toxocara cati, Toxascaris leonina, Ancylostoma tubaeforme, Taenia species and Spirometra erinacei) were detected. The total prevalence of intestinal parasite infection was significantly higher in cats aged ≤ 6 months old than in cats older than 6 months because of a significantly higher prevalence of Cystoisospora species and T cati. The total infection prevalence was higher among outdoor cats as a result of the significantly higher prevalence of T cati and S erinacei. Sex and faecal condition were not related to intestinal parasite infections. Regional differences were observed in Cystoisospora species and A tubaeforme.

Increasing water temperature and disease risks in aquatic systems: Climate change increases the risk of some, but not all, diseases

Global warming may impose severe risks for aquatic animal health if increasing water temperature leads to an increase in the incidence of parasitic diseases. Essentially, this could take place through a temperature-driven effect on the epidemiology of the disease. For example, higher temperature may boost the rate of disease spread through positive effects on parasite fitness in a weakened host. Increased temperature may also lengthen the transmission season leading to higher total prevalence of infection and more widespread epidemics. However, to date, general understanding of these relationships is limited due to scarcity of long-term empirical data. Here, we present one of the first long-term multi-pathogen data sets on the occurrence of pathogenic bacterial and parasitic infections in relation to increasing temperatures in aquatic systems. We analyse a time-series of disease dynamics on two fish farms in northern Finland from 1986 to 2006. We first demonstrate that the annual mean water temperature increased significantly on both farms over the study period and that the increase was most pronounced in the late summer (July–September). Second, we show that the prevalence of infection (i.e. proportion of fish tanks infected each year) increased with temperature. Interestingly, this pattern was observed in some of the diseases ( Ichthyophthirius multifiliis, Flavobacterium columnare), whereas in the other diseases, the pattern was the opposite ( Ichthyobodo necator) or absent ( Chilodonella spp.). These results demonstrate the effect of increasing water temperature on aquatic disease dynamics, but also emphasise the importance of the biology of each disease, as well as the role of local conditions, in determining the direction and magnitude of these effects.

First record of Calodium hepaticum and Taenia taeniaeformis liver infection in wild Norway rats (Rattus norvegicus) in Serbia

The nematode Calodium hepaticum and the cestode Taenia taeniaeformis are zoonotic helminths primarly found in the liver of common wild rats. Most reports on these helminth species with cosmopolitan distribution are from Asia, and there is paucity of data for Europe. Wild Norway rats (Rattus norvegicus) from urban and suburban habitats of the Belgrade area were examined for the presence of Calodium hepaticum and Taenia taeniaeformis larvae liver infections. The presence of visible cysts and a histomorphology of parasite-related inflammatory liver responses were sought as signs of infection. The total prevalence of infection was 10.9% (C. hepaticum) and 29.9% (T. taeniaeformis), with no differences between the sexes. No difference in the annual prevalence of both helminth species was noted. Data obtained in this study provide new information relevant to wild Norway rats as sources of C. hepaticum and T. taeniaeformis liver infection in this geographic area, and, in a wider context, in Europe. .

Interactions of Multiple Strain Pathogen Diseases in the Presence of Coinfection, Cross Immunity, and Arbitrary Strain Diversity

A model for coinfection in multiple strain infectious diseases is developed to incorporate coinfection statuses, immune and infection history, and cross immunity. It is solved for the symmetric interior equilibrium through the use of a ladder operator formalism inspired by quantum mechanical methods. We find that coinfection can fundamentally affects transmission dynamics with important epidemiologic and evolutionary consequences. It can significantly shift the distribution of age at infection for highly antigenically diverse pathogens so that in small host populations, an evolutionary strategy maximizing individual strain transmissibility might be less optimal than one which maximizes the total prevalence of all strains in the system. Alternatively, mechanisms which inhibit coinfection and thus increase total infection prevalence may be evolutionarily advantageous.

New exogenous stages of oocysts, sporocysts, and sporozoites of Goussia cichlidarum Landsberg and Paperna 1985 (Sporozoa: Coccidia) and impact of endogenous stages on the swim bladder of tilapias in Egypt

Obviously, the present study reports the coccidian parasite so-called Goussia cichlidarum for the first time in Egypt. Altogether, 25 exogenous stages were clearly distinguished from specimens of naturally infected fishes of Oreochromis niloticus, O. auraeus, and Tilapia zillii from different locations. The total prevalence of infection was about 41%. Mostly, infected fish grossly seemed with a healthy body, although severe lesions have been detected microscopically in massive infection. Portions of thick wall swim bladder have been placed in vitro. The released parasitic stages have been photographed, sketched, measured, described, and compared with previously described species. Oocysts, sporocysts, and sporozoites have also been differentiated morphologically and morphometrically. Maturity stages of sporozoites containing sporocysts within either an oocyst or those released and sporulated outside the oocyst were considerably discernible. In addition, endogenous stages have also been investigated in histological sections included gamonts, merozoites, oocysts, and different stages of sporozoites.

Haemosporidian infection in passerine birds from Lower Saxony

Blood samples from 94 coal tits (Parus ater), 56 great tits (Parus major) and 219 pied flycatchers (Ficedula hypoleuca), caught between 1993 and 2002 at two localities in Lower Saxony, Germany, were examined for haemosporidian infection by parasite-specific polymerase chain reaction (PCR). A simple PCR targeting the 18 SSU rRNA gene of the parasites was used for rapid screening of the samples and generated a total infection prevalence of 20.6% (76/369): 6.8% (n = 15) of the pied flycatchers, 19.1% (n = 18) of the coal tits and 76.8% (n = 43) of the great tits were infected. The positive specimens were re-examined by a cytochrome b gene-directed nested PCR producing significantly longer DNA fragments (approx. 520 bp) that were sequenced and analysed against GenBank-deposited nucleotide sequences. In various numbers (once to 30 times), a total of 13 parasitic DNA sequences differing from 2.9 to 8.5% (13–45 nucleotides) were demonstrated in the three bird species. Due to similarities of 98–100% with GenBank entries, 11 sequences could be assigned to Plasmodium sp. and two to the genus Haemoproteus. In summary, 57 birds were infected with Plasmodium and 19 with Haemoproteus, corresponding to 15.4 and 5.1% of all birds examined, and to 75 and 25% of all birds tested positive. As the only defined species, Haemoproteus majoris was identified in 17 great tits.

Prevalencia de infección por parásitos intestinales en escolares de primaria de Santiago de Surco, Lima, Perú

Chilomastix mesnilii (0.5%), Entamoeba coli (22.9%), Endolimax nana (19.3%), Iodamoeba butschlii (3.1%), Blastocystis hominis (12.5%), Hymenolepis nana (1.0%), Hymenolepis diminuta (0.5%), Ancylostoma duodenale - Necator americanus (1.6%), Trichuris trichiura (0.5%), Ascaris lumbricoides (1.6%), and E. vermicularis (10.4%). Total prevalence of infection, polyparasitism, helminth infection, and protozoan infection were 54.7%, 18.2%, 14.6% and 47.4%, respectively. PCA, showed in PC 1 , helminths are more relationed with presence of domestic animals, and in PC 2 , patogenic protozoan with absence of drinking water and sewage services, and with absence of animals in houses. Programs of sanitary and environmental education of coproparasites should be improved and implemented in Lima, Peru.

Substantial rise in the prevalence of Lyme borreliosis spirochetes in a region of western Germany over a 10-year period.

More than a decade after a study on the transmission cycle of Borrelia burgdorferi sensu lato in the Siebengebirge, a nature reserve near Bonn, Germany, questing nymphal and adult Ixodes ricinus ticks were collected again in three selected areas of the same low mountain range and examined for infection with B. burgdorferi sensu lato. Between May and October 2001, a total of 1,754 ticks were collected by blanket dragging; 374 ticks were analyzed for B. burgdorferi sensu lato by both an immunofluorescence assay (IFA) and at least two different PCR tests, whereas 171 ticks were analyzed by PCR only. By combining all assays, an average of 14% of the ticks tested positive for B. burgdorferi sensu lato, 5.5, 15.8, and 21.8% in the three collection areas. Of the nymphs and adults examined, 12.9 and 21.1%, respectively, were found to be spirochete infected. A lower total infection prevalence was obtained by IFA (14.4%) than by a nested PCR approach (16.5%), but both were higher than that obtained by a simple PCR approach (11.9%). Compared with data collected over a decade ago, the mean infection prevalence of B. burgdorferi sensu lato in the ticks was significantly higher for all three biotopes, whereas a similar pattern of habitat-specific infection prevalence was observed. Genotyping of B. burgdorferi sensu lato revealed high relative prevalences of B. valaisiana (identified in 43.1% of infected ticks) and B. garinii (32.3%), whereas B. afzelii (12.3%) and B. burgdorferi sensu stricto (1.5%) were relatively rare. We conclude that B. burgdorferi sensu lato infection has increased in this region over the last 15 years due to presently unknown changes in ecological conditions, perhaps related to climate change or wildlife management.

A general test of the interactive-isolationist continuum in gastrointestinal parasite communities of fish

Parasite communities are generally believed to lie somewhere along the interactive-to-isolationist continuum, i.e. from rich assemblages of species with high colonisation rates in which interspecific interactions play an important structuring role, to species-poor assemblages where interactions are unlikely. This framework has become one of the paradigms of parasite community ecology. There is, however, no objective way of ranking a set of parasite communities in terms of the extent of interactivity among their constituent species. Here, we propose a simple index of interactivity based on the general likelihood of species co-occurrence, and thus on the potential for interactions, and we apply it to component communities of gastrointestinal helminth parasites from 37 species of marine fish hosts. The index essentially collapses several features of parasite communities thought to influence the degree of interactivity into a single number independent of the number of hosts examined or the total number of species in a component community. The range of values obtained here suggests that the potential interactivity in helminth communities of fish covers almost the full spectrum of possibilities, i.e. from isolationist to highly interactive communities. Although derived from presence/absence data only, the index correlates relatively strongly with the total parasite abundance per host, as well as the total prevalence of infection and the mean infracommunity richness. In other words, it captures properties of the community that influence interactivity. The use of the index in comparative studies may help in determining whether interactive helminth communities are, as widely believed, more common in endothermic vertebrate hosts than in fish hosts.

Parasitic helminths of jumbo squid Dosidicus gigas (Cephalopoda: Ommastrephidae) in open waters of the central east Pacific

During 1981–1989, 849 jumbo squid, Dosidicus gigas, from four open ocean regions of the east Pacific (from 11°N to 22°S) were examined for parasitic helminths. The samples were collected from the Peruvian (9–21°S and 82–87°W), east equatorial (2°N–6°S and 84–87°W), west equatorial (1°N–3°S and 96–100°W) and Nicaraguan (9–11°N and 88–91°W) regions. Nine species of parasitic helminths were found, with a total prevalence of infection of 75.5%. Trematoda: metacercaria of Didymozoidae indet (prevalence: 13%, intensity: 1–35, abundance: 0.51); Cestoda: Pelichnibothrium speciosum (75.2%, 1–63 000, 664.5); Phyllobothrium sp. (1.2%, 1–2, 0.02); Tentacularia coryphaenae (6.6%, 1–5, 0.16); Nematoda: Anisakis simplex (9.2%, 1–16, 0.23); Anisakis physeteris (24.2%, 1–26, 1.22); Porrocaecum sp. (29.4%, 1–17, 0.30); Contracaecum sp. (0.5%, 1–41, 0.22); Spinitectus sp. (0.4%, 1–3, 0.01). All these parasites occurred in the larval stage. The composition of helminths and quantitative infection indexes were similar for males and females of similar mantle length (ML). Four size groups of Dosidicus were recognised. The helminths of the first size group, 30–89 mm ML comprised metacercaria of Didymozoidae and larvae of Porrocaecum sp. In the second size group, 90–139 mm ML, the prevalence of didymozoids increased to 47.5% and the majority of the parasite fauna (four species) occurred at this stage. All nine species were present in the third size group, 140–359 mm ML, but with a sharp decrease in the prevalence of didymozoids (5.8%). In the fourth size group, 360–431 mm ML, didymozoids were absent while the prevalence and intensity values for the other helminth species were maximal. The helminth fauna of similar sized squid (190–300 mm ML) from different regions was similar and the levels of infection corresponded closely. However, a comparison of ontogenetic infection dynamics between the Peruvian and east equatorial waters showed that the prevalence and intensity data for the main and secondary helminth species differed. This may support the hypothesis of isolated populations in these two regions. D. gigas is a paratenic (transport) host for the helminth species studied, with scombroid and xiphoid fishes, sharks and marine mammals as the definitive hosts.

Seasonal Fluctuations in the Occurrence of Abnormal Enlargement of the Ovary of Pacific Oyster Crassostrea gigas at Gokasho Bay, Mie, Japan.

Seasonal occurrences of the abnormally enlarged ovary of Pacific oystersCrassostrea gigascaused by an unidentified intracellular protozoan parasite was investigated in Gokasho Bay, Mie Prefecture, Japan. Cultured and wild oysters were collected bimonthly for one year from July 1996, and seasonal fluctuations in the prevalence of infection, parasite development and histological changes of the infected tissue were examined. Parasites, very similar toMarteilioides chungmuensisinfecting Pacific oysters in Korea, had 8 forms, 4 of which were frequently observed, while the other 4 forms, which were not described inM. chungmuensis, were rare. The total prevalence of infection (percentage of infected oysters positive for at least one of the two examinations : gross and smear inspections of the ovary) was usually higher than the gross prevalence of infection, indicating that infected oysters included ones without visible legions. In cultured oysters, the prevalence of infection increased in summer, suggesting that active multiplication of the parasite takes place in warm water months. From autumn through spring, no substantial change in the total prevalence of infection was observed in cultured oysters (18-20%), while it continued to decline in wild oysters during that period. These differences between cultured and wild oysters could be attributed to the oyster size and environmental factors such as salinity. Histologically, the number of infected oocytes increased in summer, but decreased in winter. From the variations in the parasite morphology and maturation of oocytes, the life cycle of the parasite and the mechanism of the legion formation are postulated.

Paramphistomum daubneyi and Fasciola hepatica: The Effect of Dual Infection on Prevalence and Cercarial Shedding in Preadult Lymnaea glabra

Preadult Lymnaea glabra measuring 4-6 mm in height were each exposed to 1 Paramphistomum daubneyi miracidium before being exposed to 1 miracidium of Fasciola hepatica. Total prevalence of infection in the snail groups from 3 different populations ranged from 33% to 39%. In each group, snails harboring larval forms of P. daubneyi, F. hepatica, or both, were noted. If the results from the 3 snail populations are pooled, the total prevalence of snail infection was 13.6% in snails harboring only F. hepatica larvae, 13% in those harboring only P. daubneyi larvae, and 10% in those with both trematodes. Cercarial shedding was obtained from snails harboring F. hepatica larval forms; in the case of snails infected with both trematodes, the mean number of metacercariae ranged from 13 to 21 for F. hepatica, and from 8 to 14 for P. daubneyi. No infected snails were found in snail groups exposed only to 1 trematode miracidia.

Prevalence of Infection with Junin Virus in Rodent Populations in the Epidemic Area of Argentine Hemorrhagic Fever

We report the results of indirect fluorescent antibody screening for antibody to Junin virus in 1,101 sera from small mammals captured on two mark-recapture grids in the epidemic area of Argentine hemorrhagic fever. Twenty-six of 29 seropositive animals were the cricetid rodent Calomys musculinus, for a 30-month prevalence of 7.9% in that species. Combining these data with previously published data on antigen detection provided an estimated total prevalence of infection of 10.9% for this, the principal reservoir species. Other infected species included two cricetids, C. laucha and Bolomys obscurus, and a predatory carnivore, Galictis cuja. Approximately half of infected animals simultaneously carried serum antibody and antigen in blood and saliva, some for 29-61 days. Except for C. laucha, which was associated with crop habitats, seropositive animals were strongly associated with the relatively rare roadside and fence-line habitats. Seropositive C. musculinus were predominantly males in the oldest age and heaviest body mass classes, and seropositive males were twice as likely to have body scars as seronegative males. These observations suggest that most infections were acquired through horizontal transmission and that aggressive encounters among adult, male C. musculinus in relatively densely populated roadside and fence-line habitats are an important mechanism of transmission of Junin virus within reservoir populations.

Junin virus activity in two rural populations of the Argentine hemorrhagic fever (AHF) endemic area.

To determine the prevalence of inapparent infection with Junin virus among the rural population and its relation to the clinical disease, a serological study was carried out in two zones of the endemic area of Argentine hemorrhagic fever (AHF). From the first appearance of AHF in the zones (1963) and the moment of the survey (1977), 14 years had passed. A total of 695 serum samples were obtained, 540 from Córdoba and 155 from Buenos Aires. Of the 695 serum samples, 83 were positive for neutralizing antibodies against Junin virus. Total infection (clinical and inapparent cases) reached 11.6% and 12.03% in the Buenos Aires and Córdoba zones, respectively, showing that the total prevalence of infection in two zones separated by 320 miles, are very much alike. In Córdoba province, the prevalence of clinical infection was 7.59%, while that for inapparent infection was 4.44%. Values for the Province of Buenos Aires were 9.67% and 1.93%, respectively. In addition to a low prevalence of inapparent infections, the results of this survey show that roughly 90% of the population is susceptible to contract the disease; this stresses the need to immunize susceptible individuals in the endemic area.