Enzootic Regions Research Articles

Genetic diversity and relationships among Venezuelan equine encephalitis virus field isolates from Colombia and Venezuela.

During field studies of enzootic Venezuelan equine encephalitis (VEE) viruses associated with epizootic emergence, a large number of virus isolates were made in sylvatic foci of Venezuela and Colombia. To rapidly characterize these isolates, antigenic subtypes were determined by means of immunofluorescence and by single-strand conformational polymorphism (SSCP) analysis by use of an 856-bp fragment from the P62 gene, which we used to distinguish genetic variants. Representative isolates were sequenced to assess the sensitivity of SSCP to detect genetic differences. The SSCP analysis distinguished isolates differing by as little as 1 nucleotide; overall, differences of > or = 1 nucleotide were recognized 89% of the time, and the sensitivity to distinguish strains that differed by only 1 or 4 nucleotides was 17 and 57%, respectively. Phylogenetic analyses of representative sequences showed that all recent isolates from the Catatumbo region of western Venezuela and the middle Magdalena Valley of Colombia were closely related to epizootic subtype IAB and IC strains; strains from Yaracuy and Miranda States were more distantly related. Cocirculation of the same virus genotype in both Colombian and Venezuelan foci indicated that these viruses are readily transported between enzootic regions separated by > 300 km. The SSCP analysis appears to be a simple, fast, and relatively efficient method of screening VEE virus isolates to identify meaningful genetic variants.

Canine antibody response to Blastomyces dermatitidis WI-1 antigen

To assess whether dogs with blastomycosis produce antibodies against the WI-1 and A-antigens of Blastomyces dermatitidis and whether the antibodies are useful in serodiagnosis. 359 serum samples obtained from 245 dogs. 233 samples from 122 dogs with blastomycosis, and 1 sample each from 24 dogs with suspected blastomycosis, 51 control dogs without infection, and 48 healthy dogs from an enzootic region were obtained. Antibodies against WI-1 antigen were detected by radioimmunoassay (RIA). Serum samples were tested in parallel for antibodies against the A-antigen of B dermatitidis by commercial agar-gel immunodiffusion (AGID) in a reference laboratory. Antibodies were detected in 92% of infected dogs by RIA and in 41 % by AGID. For 29 serum samples that were obtained 11 to 1,545 days after diagnosis, antibodies were detected in 92% of samples by RIA and 7% by AGID. For 93 serial serum samples from 29 dogs with blastomycosis, the mean anti-WI-1 titer was 1:18,761 at the time of diagnosis, and decreased to a mean of 1:1,338 by 210 days after treatment was initiated. Of 24 dogs with suspected infection, antibodies were detected in 67% by RIA and 33% by AGID. Control dogs without blastomycosis had no detectable antibodies in either assay. Thus, sensitivity was 92% for RIA and 41 % for AGID, and specificity was 100% for both tests. Anti-WI-1 antibodies are readily detected by RIA in dogs with blastomycosis. Titers become high, decline during treatment, and persist for months. Anti-A antibodies are sometimes detected with AGID, but these decrease quickly.

Clinical, clinico-pathological and serological studies of Babesia ovis in experimentally infected sheep.

Clinical, clinico-pathological and serological studies were performed in sheep experimentally infected with Babesia ovis. Acute babesiosis occurred in all the lambs infested with adult Rhipicephalus bursa ticks and in one lamb infested with the larvae. The rate of parasitaemia and the degree of anaemia were not correlated. Decrease in the packed-cell volume ranged from 30 to 40%. Parasitized erythrocytes were not observed to block capillaries in the brain, which explained the absence of nervous symptoms in acute babesiosis. The kidneys were the most severely affected organs, exhibiting acute glomerulonephritis. The lesions observed were suggestive of vascular alteration and vascular stasis, leading to anoxia of the tissues. A disseminated intravascular coagulation (DIC) syndrome was recorded in sheep infected with babesiosis. A marked increase in the enzymes of the transaminase groups, mainly aspartate aminotransferase (AST), was observed. Enzymatic changes (increases in AST, alanine aminotransferase (ALT) and lactic dehydrogenase (LDH) and decreases in sorbitol dehydrogenase (SDH), alkaline phosphatase (ALP) and malic enzyme (MEZ)), decreases in total proteins and albumin, and increases in urea and creatinine might reflect the degree of severity of the damage to the liver and kidney tissues. Most of the lambs (85%) that were infested with larvae, and all lambs infested with adult R. bursa ticks, reacted serologically to B. ovis antigen. The serological reactions following infestation with the larvae occurred much later than those following infestation with the adult stage. The lambs which were infested with larvae showed mild clinical reactions when challenged by infected R. bursa adults, as compared with the reactions to the challenge in naive control animals. The serological findings, in addition to the fact that one splenectomized lamb reacted to larval infestation with acute ovine babesiosis, show that the preimaginal stages of R. bursa can transmit B. ovis, usually causing a sub-clinical disease. It is suggested that infections derived from preimaginal ticks in the winter can preimmunize sheep for the subsequent more severe infections derived from adult ticks in the summer. Furthermore, in the absence of a reliable vaccine against B. ovis, grazing flocks in the enzootic regions should be exposed to the preimaginal stages during their activity period (October-February) before exposure to the adult ticks in spring and summer (April-July).

Evaluation of fox-chasing enclosures as sites of potential introduction and establishment of Echinococcus multilocularis.

Following detection of Echinococcus multilocularis in red foxes (Vulpes vulpes) illegally imported into South Carolina (USA) for release in fox-chasing enclosures, a survey for E. multilocularis was conducted in four enclosures in Georgia (USA) and six enclosures in South Carolina. Survey methods included examination of potential small mammal intermediate hosts (n = 390) for E. multilocularis larvae, examination of fox and coyote (Canis latrans) scats (n = 59) for taeniid eggs, and examination of one possible canine definitive hosts for adult E. multilocularis. All intermediate and definitive hosts examined were negative for E. multilocularis and taeniid eggs were not recovered from fox and coyote fecal samples. Thus, E. multilocularis may not yet be established in fox-chasing enclosures in Georgia and South Carolina. Despite the failure to demonstrate E. multilocularis in the fox-chasing enclosures surveyed, translocation of wild canids from known enzootic regions should be discouraged because E. multilocularis is known to be ecologically adaptable and because contact with potentially infected definitive hosts during translocation is a public health risk.

Large-scale use of liquid-phase blocking sandwich ELISA for the evaluation of protective immunity against aphthovirus in cattle vaccinated with oil-adjuvanted vaccines in Argentina

Specific serum activity levels against four reference strains of foot-and-mouth disease virus (FMDV) were evaluated from 1634 animals vaccinated with commercial quadrivalent oil vaccines and from 746 unvaccinated, naive animals, using the liquid-phase blocking sandwich ELISA (lpELISA) test. Cows from the FMDV-free area of Argentina were tested for the absence of specific FMDV antibodies (sp FMDV Abs) and those showing lpELISA titres <1.0 were grouped in lots of 16 animals. They were vaccinated and challenged at 90 days postvaccination (DPV) with one of four virus strains used for vaccine production and control (prototype strains). Serum samples from vaccinated and control cattle were collected 60 and 90 DPV and the level of sp FMDV Abs was determined by lpELISA. Animals were examined for clinical signs of disease. Results show that serum lpELISA titre levels directly correlate with the percentage of protected animals. It was seen that 100, 98, 93 and 87% of the vaccinated cattle with antibody titre levels ⩾2.1 were protected against challenge with serotypes C85, A87,01 Cas and A79, respectively. Evidence is also presented of seroconversion in a sample of 3–5-month-old calves vaccinated in the field, showing lpELISA titres compatible with protection against the four vaccine viruses as long as 150 DPV. Results reported in this paper strongly support the use of the lpELISA test for a rapid and reliable evaluation of the efficacy of FMDV commercial vaccines as well as for the assessment of the immunological status of cattle in FMDV-free and enzootic regions of South America.

Diversionary Role of Hoofed Game in the Transmission of Lyme Disease Spirochetes

To determine whether the presence of ungulates may inhibit transmission of the agent of Lyme disease (Borrelia burgdorferi) while promoting the abundance of its European vector tick (Ixodes ricinus), we compared the feeding density of subadult ticks on roe deer (Capreolus capreolus), red deer (Cervus elaphus), fallow deer (Dama dama), and wild sheep (Ovis ammon) near Berlin and in Brandenburg State, Germany. The prevalence of spirochetal infection in these ticks was compared with that in ticks swept from nearby vegetation. Spirochetes are present in nearly one-fifth of nonfed, questing nymphal and adult wood ticks in the region. Many ungulates in this intensely enzootic region fail to mount a detectable humoral response against the agent of Lyme disease, even when exposed to numerous infected ticks. During the height of the summer, each ungulate may support the feeding of hundreds of subadult ticks. Larvae feed lower on the bodies of hoofed game than do nymphs. Few ticks retain infection by the Lyme disease spirochete after feeding on hoofed game animals. We conclude that numerous I. ricinus ticks feed on ungulates, but that such host-contact fails to infect these ticks while eliminating pre-existing spirochetal infection.

A prospective study of vesicular stomatitis in cattle in an enzootic region of Mexico

A prospective study of vesicular stomatitis was conducted in two bovine herds in southeastern Mexico. In July 1987, an initial serological screening showed that 64% and 87% of the 654 cattle tested negatively to vesicular stomatitis New Jersey and Indiana antibodies, respectively, using the plaque-reduction serum neutralization test. Most seropositive animals were at least 24 months of age. Based on the initial serological screening, cohorts of seronegative and seropositive cattle were monitered (January–December 1988) for the prevalence of vesicular stomatitis virus (VSV) antibodies using an enzyme-linked immunosorbent assay (ELISA). The serological results, using ELISA, indicated that no VSV activity occured in the two study herds. The seronegative cohort of cattle did not yield a positive seroconversion pattern to either VSV Indiana or New Jersey. The seropositive cohort showed a variable antibody response pattern against the VSV. There were no clinical cases of vesicular stomatitis (VS) in the two herds. The data from the national surveillance program for vesicular diseases suggested that 1988 was a year of low VSV infection incidence in southeastern Mexico.

Evaluation of an enzyme-linked immunosorbent assay for detection of antibodies to vesicular stomatitis virus in cattle in an enzootic region of Mexico

Summary An elisa was compared with the plaque-reduction serum neutralization (prsn) test, for detection of vesicular stomatitis virus (vsv) antibodies in cattle in a vesicular stomatitis enzootic region of Mexico. A total of 325 bovine serum samples were screened for vsv antibodies. The prsn test was performed, using Vero cells. The elisa contained gradient-purified vsv Indiana (Lab strain) and vsv New Jersey (Hazelhurst) as the antigens. Regression analysis and weighted kappa statistic were used to estimate measures of agreement between the 2 assays for detection of vsv antibodies. The elisa method proved useful for sero-diagnosis of vesicular stomatitis The elisa and prsn test results were highly correlated for detection of vsv antibodies.

Polymerase errors accumulating during natural evolution of the glycoprotein gene of vesicular stomatitis virus Indiana serotype isolates

We report the entire glycoprotein (G) gene nucleotide sequences of 26 vesicular stomatitis virus Indiana serotype (VSV IND) type 1 isolates from North and Central America. These sequences are also compared with partial G gene sequences of VSV IND type 2 (Cocal) and type 3 (Alagoas) viruses and the complete G gene sequences of the more distantly related VSV New Jersey (NJ) and Chandipura viruses. Phylogenetic analysis of the G gene sequences by maximum parsimony revealed four major lineages or subtypes within the classical VSV IND (type 1) viruses, each with a distinct geographic distribution. A high degree of VSV genetic diversity was found in Central America, with several virus subtypes of both VSV IND and NJ serotypes existing in this mainly enzootic disease region. Nineteen percent sequence variation but no deletions or insertions were evident within the 5' noncoding and the coding regions of the VSV IND type 1 G genes. In addition to numerous base substitutions, the 3' noncoding regions of these viruses also contained numerous base insertions and deletions. This resulted in striking variation in G gene sizes, with gene lengths ranging from 1,652 to 1,868 nucleotides. As the VSV IND type 1 subtypes have diverged from the common ancestor with the NJ subtypes, their G mRNAs have accumulated more 3' noncoding sequence inserts, ranging up to 303 nucleotides in length. These primarily consist of an imprecise reiteration of the sequence UUUUUAA, apparently generated by a unique polymerase stuttering error. Analysis of the deduced amino acid sequence differences among VSV IND type 1 viruses revealed numerous substitutions within defined antigenic epitopes, suggesting that immune selection may play a role in the evolution of these viruses.

Serological Monitoring of Vesicular Stomatitis New Jersey Virus in Enzootic Regions of Costa Rica

The activity of vesicular stomatitis viruses was monitored on 3 dairy farms in Costa Rica. Antibody levels were measured and clinical disease monitored in 165 cattle during a 20 month period (1986-1988). Vesicular stomatitis New Jersey (VS NJ) virus was shown to be enzootic on these farms by a 94.2% prevalence of neutralizing antibody; this did not vary significantly between herds. The mean prevalence of antibody to vesicular stomatitis Indiana (VS IN) virus was 15.2%, but was significantly higher in 1 herd. A total of 25 cases (annual incidence rate of 9%) of clinical vesicular stomatitis (VS) was reported. VS NJ virus was identified as the causal agent by detection of VS NJ virus antigens by the complement fixation test. VS NJ virus was isolated in 11 cases. All episodes of disease occurred between November and January, the beginning of the dry season. Most animals maintained stable neutralizing antibody titers throughout the study, and all diseased animals were previously seropositive to VS NJ virus. A total of 31 animals with neutralizing antibodies to VS NJ virus had a VS NJ virus-specific IgM response, and 6 animals had IgM responses that persisted for as long as 6 months. There was no relation between IgM responses and clinical disease occurrence. VS NJ virus persisted predominantly as a subclinical infection in cattle throughout the year in enzootic areas of Costa Rica. The humoral response did not prevent reinfection with VS NJ virus.

Spontaneous mutations leading to antigenic variations in the glycoproteins of vesicular stomatitis virus field isolates

Strains of vesicular stomatitis virus, New Jersey serotype (VSV-NJ), isolated from diseased cattle or swine were examined by genomic RNA sequencing for genetic diversity potentially leading to antigenic variations in their type-specific glycoproteins as determined by reactivity with epitope-specific monoclonal antibodies (MAbs). Seven field isolates recovered in Colorado, New Mexico, Georgia, and Mexico during the widespread 1982–1985 epizootic in the western United States resembled the prototypic 1952 Hazelhurst subtype by partial sequence homology, but amino acid reversions to the 1949 Ogden subtype occurred frequently. When studies were performed with MAbs directed to the Ogden subtype glycoprotein, relatively limited antigenic variation, and only in neutralization epitope VIII, was noted among two of five epizootic isolates from Colorado and New Mexico. However, amino acid differences in the glycoprotein of a 1983 isolate from an enzootic region of Georgia resulted in major antigenic deficiencies in epitopes V, VI, and VII as determined by Western blotting and neutralization of infectivity with epitope-specific MAbs. Quite a few genetic but no antigenic differences were noted in an enzootic 1984 isolate from Mexico, a potential origin of the United States epizootic. Marked or complete loss of epitopes VII, VI, VIII, and V can be traced to spontaneous mutations leading to amino acid substitutions at glycoprotein positions 199, 263, 275, and 317, respectively, in the enzootic Georgia isolate 07/83-GA-P and the epizootic New Mexico isolate 06/85-NM-B. By comparison, closely adjacent amino acid substitutions at glycoprotein positions 210, 268, 277, and 364 occurred in epitope-deficient mutants selected for resistance to neutralization by MAbs specific for epitopes VII, VI, VIII, and V, respectively. Two neutralization epitopes designated X and XI were found to be unique for the G protein of the 1952 Hazelhurst isolate … /52-GA-P. The epitope X-specific MAb H21, in particular, failed to neutralize the infectivity not only of the Ogden subtype …/49-UT-B but also was ineffective against all the 1982–1985 field isolates. The classical 1952 Hazelhurst strain of VSV-NJ is genetically and antigenically quite different from those viruses isolated during the 1982–1985 epizootic.

Experimental plague infection in South African wild rodents.

Susceptibility studies were undertaken to determine the response of some South African wild rodent species to experimental plague (Yersinia pestis) infection. A degree of plague resistance was found in three gerbil species captured in the plague enzootic region of the northern Cape Province, these being the Namaqua gerbil, Desmodillus auricularis, (LD50 1 X 10(6) organisms), the bushveld gerbil, Tatera leucogaster, (LD50 9.1 X 10(5)) and the highveld gerbil, T. brantsii (LD50 4 X 10(2)). Animals from a population of the four-striped mouse, Rhabdomys pumilio, captured in the plague area of Port Elizabeth, proved moderately resistant to experimental plague infection (LD50 1.3 X 10(4)) while those from another population of the same species captured in a plague-free area of the Orange Free State were extremely susceptible (LD50, 5 organisms). The response of both populations however was a heterogeneous one. Marked differences in susceptibility were also found between two populations of multimammate mice, Mastomys natalensis (2n = 32) although both originated from areas outwith the known distribution of plague in southern Africa. The 50% infectious dose was relatively high in T. leucogaster (3.2 X 10(2)) and D. auricularis (1.7 X 10(3)), but was low (2-16 organisms) in the other rodent species tested. The plague antibody response, determined by enzyme-linked immunosorbent assay (ELISA), was extremely short-lived in T. leucogaster, only 10% of inoculated animals remaining seropositive at low titres after 11 weeks. Antibodies persisted for only slightly longer in the sera of T. brantsii which were reinoculated with 2 X 10(3) plague organisms 6 weeks after initial challenge. The demonstration of the existence of both susceptible and resistant populations of R. pumilio and M. natalensis indicates that these species must be considered as potential plague reservoir hosts in parts of South Africa. The results suggest that resistance to plague infection in previously epizootic hosts in the northern Cape Province such as Tatera sp. and D. auricularis has arisen through continual selective pressure of the organism. If the findings are applicable to gerbil populations in other plague enzootic regions of South Africa it is probable that acquired plague resistance has been responsible for the absence of gerbil epizootics and consequently for the dramatic decline in human plague outbreaks in South Africa since 1950.

Natural La Crosse Virus Infection in the Red Fox (Vulpes Fulva), Gray Fox (Urocyon Cinereoargenteus), Raccoon (Procyon Lotor), and Opossum (Didelphis Virginiana) *

Natural infection of sentinel red foxes (Vulpes fulva) and free-ranging red foxes, gray foxes (Urocyon cinereoargenteus) and raccoons (Procyon lotor) with La Crosse (LAC) virus was demonstrated. One isolate of LAC virus was obtained from a sentinel red fox in an enzootic area. The viremia titer of the LAC virus-infected red fox was above the threshold of infection for Aedes triseriatus mosquitoes. Antibody responses were measured by the microneutralization test employing four California group viruses: LAC, snowshoe hare, trivittatus, and Jamestown Canyon. Four of six sentinel red foxes developed LAC virus neutralizing antibody. Antibody titers peaked between days 7 and 34 and were still detectable by dat 345 post-infection. Homologous LAC virus antibody titers were consistently 4-fold or greater than heterologous titers. Serological evidence for natural LAC virus infection was demonstrated in 33 of 57 (58%) free-ranging red foxes, 18 of 32 (57%) gray foxes, and 4 of 16 (25%) raccoons. Antibody titers were comparable in free-ranging foxes infected naturally and those infected experimentally by mosquito bite. The prevalence of infection was significantly different (P less than 0.001) for foxes trapped on three distinct areas within the enzootic region. Rates of infection in foxes by area coincided with LAC virus antibody prevalence observed in free-ranging chipmunks and with reported cases of human LAC encephalitis in Wisconsin.

Mortality among cattle and buffaloes in Sri Lanka due to haemorrhagic septicaemia.

Data on the mortality of cattle and buffaloes in 62 epizootics of haemorrhagic septicaemia (HS) in the HS enzootic and non-enzootic regions of Sri Lanka was collected and subjected to statistical analysis. It was found that the overall mortality for buffaloes was higher than for cattle (45.2 and 15.8% respectively, P less than 0.001). For buffaloes in enzootic areas only the overall mortality was 29% whilst in non-enzootic areas it was 64.5% (P less than 0.05). In the enzootic areas deaths were mainly confined to young animals whereas in the non-enzootic areas when sporadic outbreaks of HS occurred deaths were scattered over all age groups. The vaccines used, vaccination schedules adopted and the coverage of vaccination in these herds did not appear to influence the mortality among buffaloes in enzootic areas to a statistically significant degree.

Methods for Detecting Babesia microti Infection in Wild Rodents

We compared various methods for detecting Babesia microti infection in white-footed mice (Peromyscus leucopus) captured in enzootic regions of Massachusetts. The most sensitive method tested involved inoculating blood from wild rodents into hamsters. One month postinoculation proved to be the optimal time for microscopically examining blood of inoculated hamsters. With this method, as few as 300 organisms produced patent infection. Prior splenectomy of hamsters did not increase susceptibility to infection. For direct study of captured animals, a Giemsa-stained, thin blood-film prepared from the animal's tail was the most convenient method tested. However, this method detected only 61% of infections identified by hamster inoculation.

Natural infections of Richardson's ground squirrels with western equine encephalomyelitis virus, Saskatchewan, Canada, 1964-1973.

A survey (1964-1973) was conducted on naturally occurring western equine encephalomyelitis (WEE) virus infections of Richardson's ground squirrels (RGS) in agricultural areas of Saskatchewan. The survey included both serology and virus isolation attempts on live-trapped wild squirrels. Throughout the study, seropostive squirrels were found in the known enzootic regions of the province each summer. The infections rate was high (11.6% of 250) in the epidemic year of 1965 and low (less than 2% of 681) in the subsequent non-epidemic years. The maximal seasonal prevalence of seropositive RGS coincided with the time when the squirrel population and aedine mosquito abundance reached their seasonal peaks. Five virus isolations were obtained from the blood and brains of naturally infected squirrels. All isolations were from squirrels collected in June. The early seasonal infections in squirrels could provide a source of virus for Culex tarsalis, the epidemic vector. In view of their abundance in the enzootic agricultural areas and the high annual population turnover, the RGS may play an important role in the natural history of WEE virus in the Canadian prairies.

Malignant theileriosis of sheep and goats

Clinical, pathological and epizootiological studies were carried out in an experimental flock of 39 sheep that was exposed to natural infection ofTheileria hirci in an enzootic area. A morbidity rate of 100 per cent and a mortality rate of 89.74 per cent were observed in this flock which had been transferred from another enzootic region. NoTheileria hirci infection was observed, during the same period, in the control sheep which were sprayed regularly. The high morbidity and mortality rate in the flock might have been due to the existence of antigenically different strains in different localities. Almost all the ticks collected from the sheep during the course of the study wereHyalomma spp.

Studies on bovine besnoitiosis in Korea: II. A survey on incidence in the enzootic region.

The 4,725 cattle in the enzootic region, 6 counties of southern Korea, were surveyed for besnoitiosis epidemiologically by examining the scleral conjunctiva for the cysts and the following results were obtained. The survey showed that 285 cattle, representing 6 per cent of a total of 4,725 cattle examined had S.C. cysts. Only 49 (14 per cent) of them showed clinical sclerodermatitis and the ratio between clinical and inapparent cases was 1:5.8. On age distribution of the S.C. positive cases the highest incidence(10-12 per cent) was seen in amimals that were from 5 to 8 years of age, but clinically apparent cases occurred much more in younger age of animal. In local incidence of S.C. cysts positive cases the prevalence was higher in the secluded districts such as Koheung and Sancheoung counties(9 per cent).

Temperature and humidity in the microhabitat of rodent fleas in Hawaiian cane fields.

Hawaiian sugar cane fields, in the enzootic plague region, offer a nearly stable temperature and humidity for fleas associated with the infection. In occupied rodent nests in boxes, host body heat raised the temperature above that of the surrounding soil which is determined by climate, not weather, and cane cover. Moderate temperature and high per cent relative humidity in nests were always suitable for breeding by the most abundant rodent flea in the fields, Xenopsylla vexabilis.

Observations on Trypanosoma lewisi and Grahamella sp. in the Blood of Rats from the Hamakua District, Island of Hawaii

During the course of an investigation on wild rodent flea control in the enzootic plague region of the Island of Hawaii, observations were made on Trypanosoma lewisi in several species of rats inhabiting a wild gulch area of the Hamakua District. These observations were not the result of an organized study of blood parasites, since the original purpose of the investigation was to use T. lewisi as an indicator of the pulicidal effect of insecticides affecting rat fleas. It was thought that a significant reduction in the rat flea population would be reflected by a declining curve of new trypanosome infections in young susceptible rats. Unfortunately, the field investigations did not last long enough to allow an adequate evaluation of the above hypothesis. A search of the literature has not revealed any reports on the blood protozoa of rats in the Hawaiian Islands. Furthermore, no evidence has been found on the incidence of blood protozoa in commensal rat species living in wild situations. Recent studies by Eyles (1952) and Calero (1952) review evidence on the incidence of Trypanosoma lewisi in rats from the American continent. Seven different studies cited by these authors, and their own investigations, show the incidence of T. lezwisi in the Norway rat to vary from 0.5 to 47.5 percent. On the contrary, a study in Quebec, Canada, failed to demonstrate any blood protozoa in the brown rat (Firlotte, 1948). As far as can be determined, there is scant information on blood parasites of the black rat and its subspecies. Swellengrebel (1913) presented data on T. lewisi in Rattuzs rattus rattus in Eastern Java; all of his data were based on rats with a body length under 150 mm. Dore (1918) found 30% of R. norvegicus from sewers and 12% from wharves and grain stores infected with 7'. lewisi in Auckland, New Zealand. This author also suggested that in New Zealand Rattus exulans, a member of the group to which the Hawaiian rat belongs, declined in numbers due to infection with T. lewisi. If this hypothesis is true it would substantiate the idea that T. lewisi is a relatively new parasite in rats of the Malaysian concolor group. Laird (1951) obtained 65 R. norvegicus from buildings in Wellington, New Zealand and found 3 individuals infected with T. lewisi. The average dimensions of 100 trypanosomes recorded by this author are in substantial agreement with the mensural data given in the present report. The present note will record observations on Trypanosoma lewisi mainly in the Hawaiian rat, Rattus hawaiiensis, in subspecies of the black rat, primarily Rattus rattus alexandrinus, and to a lesser extent in R. norvegicus. Data also are presented here on an apparently unknown species of Grahamella