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PubMed1993

Involvement of dogs in plague epidemiology in Tanzania. Serological observations in domestic animals in Lushoto District.

Venous blood was collected aseptically from clinically healthy domestic dogs, goats, sheep, cats and fowl in various plague-infected villages of Lushoto District, Tanzania, at the time when the disease was actively prevalent in the area. Flea ectoparasites were collected from the animals, processed, identified and counted. Serum samples were tested for specific plague antibodies, using the passive haemagglutination technique and checked by passive haemagglutination inhibition tests. Altogether 389 animals, of which 201 were domestic dogs, were involved. 11 (5.5%) dogs had significantly elevated specific plague antibodies at titres ranging from 20 to 1280. All the dogs were also heavily infested with fleas at a mean index of 7.7 fleas per animal. Of 1,871 fleas collected from the dogs, 93.8% were Ctenocephalides felis and 6.2% were C. canis. All the other animals examined were negative for plague. It was concluded that domestic dogs could play an important role as plague carriers in the area and that the animals could serve as sentinel animals for the detection of plague in villages where human plague outbreaks have not previously occurred.

Animals↗
PubMed1981

Experimental infection of ectoparasitic arthropods with Rickettsia prowazekii (GvF-16 strain) and transmission to flying squirrels.

Epizootiologic studies conducted during the past few years showed the existence of widespread natural infection of the southern flying squirrel, Glaucomys volans, with epidemic typhus rickettsiae, Rickettsia prowazekii. The ecological findings strongly implicated transmission of the etiologic agent by an arthropod vector. Studies were conducted under controlled laboratory conditions to determine whether ectoparasites naturally associated with flying squirrels (squirrel fleas, lice, mites and ticks) were capable of acquiring, maintaining and transmitting the infection. Also studied were the cat flea, oriental rat flea and the human body louse. Flying squirrels inoculated with the GvF-16 strain of R. prowazekii circulated rickettsiae in their blood for 2-3 weeks, thus providing ample opportunity for arthropods feeding on them to become infected. The results with Dermacentor variabilis ticks indicated that the rickettsiae did not consistently survive in this insect and were not passed to the eggs of adult females that had been infected subcuticularly. Mites became infected by feeding on infectious blood but failed to sustain the infection. Also, mites fed on an infected flying squirrel did not transmit the infection to a normal squirrel. Squirrel, cat, and oriental rat fleas readily became infected by feeding on a rickettsemic host or on infectious blood through membranes, but failed to transmit the infection to susceptible flying squirrels. In the studies with flying squirrel lice, however, transmission of epidemic typhus from infected to uninfected flying squirrels was demonstrated. Infection of the human body louse with the GvF-16 flying squirrel strain of R. prowazekii was similar to that previously observed with classical human strains, viz., multiplication of the rickettsiae and excretion in the feces.

Animals↗
PubMed2006

Observations on the endemicity of plague in Karatu and Ngorongoro, northern Tanzania.

Commensal and field rodents and wild small carnivores were live-trapped in five villages of Karatu district and one settlement in the Ngorongoro Conservation Area in Ngorongoro district in Tanzania. Blood samples were taken and serologically tested for plague, using the Blocking ELISA technique. Some domestic dogs and cats in the Karatu villages were aseptically bled and similarly tested for plague. Fleas were collected from the examined animals and from randomly selected residential houses. A total of 241 rodents, 1 Crocidura spp, 43 dogs, 12 cats and 4 slender mongooses were involved in the survey. Of the rodents, 14.5% were infested with fleas, which comprised of Xenopsylla brasiliensis (45.8%) and Dinopsyllus lypusus (54.2%), with an overall population density of 0.2 fleas/animal. Thirty one (72.1%) of the dogs were infested with fleas, all of which were Ctenocephalides spp. Thirty five (63.3%) houses were infested with fleas whose population was composed of Ctenocephalides spp, Pulex irritans, Tunga penetrans and Echinophaga gallinacea. Infected rodents were found in all the villages while the infected dog was found at Rhotia-Kati. Nineteen (11%) of the rodents and one (2%) dog harboured specific plague antibodies. It was broadly concluded that sylvatic plague was endemic in Karatu district and Ngorongoro Conservation Area and that outbreaks of the disease can occur in the area any time if and when relevant conditions become favourable. Prompt application of appropriate preventive and control measures and survey for substantiating the status in the Lake Manyara National Park, which is adjacent to some of the infected villages, are recommended.

Animals↗
PubMed2006

No evidence of persistent Yersina pestis infection at prairie dog colonies in north-central Montana.

Sylvatic plague is a flea-borne zoonotic disease caused by the bacterium Yersinia pestis, which can cause extensive mortality among prairie dogs (Cynomys) in western North America. It is unclear whether the plague organism persists locally among resistant host species or elsewhere following epizootics. From June to August 2002 and 2003 we collected blood and flea samples from small mammals at prairie dog colonies with a history of plague, at prairie dog colonies with no history of plague, and from off-colony sites where plague history was unknown. Blood was screened for antibody to Y. pestis by means of enzyme-linked immunosorbent assay or passive hemagglutination assay and fleas were screened for Y. pestis DNA by polymerase chain reaction. All material was negative for Y. pestis including 156 blood samples and 553 fleas from colonies with a known history of plague. This and other studies provide evidence that Y. pestis may not persist at prairie dog colonies following an epizootic.

Animals↗
PubMedDate not supplied

[The action of anticoagulants on the transmission of the causative agent of plague].

The anticoagulants 4-hydrocoumarine and 1,3-indandione derivatives produce a varying action on the formation of a gizzard block in plague-infected fleas. The feeding of fleas on the animals having typical signs of severe intoxication with ratindane, zoocoumarine, and tomorine reduces the time and incidence of gizzard block formation in the fleas. The individuals with blocks retain their high infectability and the development of an infectious process is mainly generalized in rodents. In this connection, the package of eradication measures should involve the concurrent use of insecticides and zoocides which can reduce the size of both rodents and fleas.

Animals↗
PubMed2000

Rodent ectoparasites from two locations in northwestern Florida.

From Feb.-Apr. 1999, 19 species of ectoparasitic arthropods (2 sucking lice, 4 fleas, 4 ticks, 2 mesostigmatid mites, 5 chiggers, 2 fur mites) were recovered from 106 rodents belonging to 5 species (cotton mouse, Peromyscus gossypinus, n = 64; cotton rat, Sigmodon hispidus, n = 23; eastern woodrat, Neotoma floridana, n = 9; golden mouse, Ochrotomys nuttalli, n = 9; eastern gray squirrel, Sciurus carolinensis, n = 1) at Tall Timbers Research Station, Leon County, Florida. During the same period, 13 species of ectoparasites (2 sucking lice, 1 flea, 3 ticks, 3 mesostigmatid mites, 2 chiggers, 2 fur mites) were recovered from 57 rodents belonging to 3 species (S. hispidus, n = 40; black rat, Rattus rattus, n = 16; S. carolinensis, n = 1) from Panama City, Bay County, Florida. Noteworthy ectoparasite records include Ixodes minor from both sites, which extends the known geographical range of this tick, and Stenoponia americana from Tall Timbers that represents the second documented Florida record of this flea. Potential tick vectors (Dermacentor variabilis and Ixodes scapularis) of zoonotic pathogens (Rickettsia rickettsii and Borrelia burgdorferi) were collected at both sites. On S. hispidus, fleas were more prevalent at Tall Timbers but sucking lice, chiggers, ticks, mesostigmatid and listrophorid mites all were more prevalent at the Panama City site. Arthropods recovered from arboreal nests (n = 3) of O. nuttalli at Tall Timbers included 3 species of ectoparasites (1 tick, 2 laelapid mites).

Animals↗
PubMedDate not supplied

[Life expectancy of Ctenophthalmus wladimiri Is.-Gurv., 1948 (Siphonaptera, Ctenophthalmidae) under laboratory conditions].

Laboratory studies have shown that at 75% humidity fleas, Ct. wladimiri, are less viable than at 100% humidity. At 100% humidity at a temperature from 0 to 10 degrees and without feeding newly born imagos survived up to 363 days, at a higher temperature from 18 to 30 degrees-from 44 to 163 days. At a temperature from 7 to 10 degrees imagos, which fed one time, lived up to 355 days and at 0 to 2 degrees-up to 287 days. Maximum life duration (1133 days) for periodically feeding fleas was at 100% humidity at a temperature from 7 to 10 degrees. Under such conditions 50% of fleas survived up to 114 days. Hungry but previously "prepared" for winter fleas lived at a temperature from 0 to 2 degrees not more than 376 days.

Adipose Tissue↗
PubMed2002

Efficacy of two 65 % permethrin spot-on formulations against canine infestations of Ctenocephalides felis and Rhipicephalus sanguineus.

The efficacy of two formulations of a topically applied 65% permethrin spot-on for dogs (Defend EXspot Treatment for Dogs, Schering-Plough Animal Health Corp.) was evaluated against experimental infestations of the cat flea, Ctenocephalides felis, and the brown dog tick, Rhipicephalus sanguineus. Thirty dogs were randomly allocated to treatment with 65 % permethrin in diethylene glycol monomethyl ether (original formulation), 65 % permethrin in propylene glycol monomethyl ether (test formulation), or to an untreated control group. Dogs assigned to treatment with a permethrin formulation received either 1 or 2 ml of the formulation in accordance with label directions on Day 0. One hundred unfed, adult cat fleas and 50 unfed, adult ticks were placed on each dog on Days -1, 5, 12, 19, 26, 33, and 40. Live fleas and ticks were counted on each dog on Days 2, 7, 14, 21, 28, 35, and 42. Treatment of dogs with either formulation of 65 % permethrin significantly (P <.05) reduced the number of live fleas and ticks from Days 2 through 42. No statistical differences were noted between the formulations regarding efficacy against C. felis or R. sanguineus.

Administration, Topical↗
PubMed2001

[The plague at the Tsenabe Isotry market in Antananarivo: a complex epidemiologic situation].

The transmission of Yersinia pestis is intense among rats in the wholesale market Tsenabe Isotry in the capital Antananarivo (anti-F1 sero-prevalence 80%, flea index 8.4 for a cut-off risk index of > 1). However, the number of plague-suspected (not laboratory confirmed) human cases has only been 3 in this district during a four years period from 1995 to 1999. A seroepidemiological survey among the market vendors was undertaken in June 1999 to test the hypothesis that the low incidence of human plague is due to acquired immunity. In addition, surveillance of the rat and the flea populations in the market was carried out. Only 3 (3.2%) of 95 screened vendors were anti-F1 IgG positive, whereas the markers of plague transmission among rodents and fleas were still high. This result suggests that the low incidence of human plague was not due to acquired immunity but to other factors such as the limited contact between humans and the rat fleas because of the abundance of rats, the absence of epizootic due to the resistance of rats in the capital and a particular behaviour of the predominant rat Rattus norvegicus.

Adolescent↗
PubMed2001

[Evaluation of the effect of Knox-Out microencapsulated V.O. 240 and K-othrine powder on rat lice in two villages in the Betafo region].

The effect of two different insecticides on flea control was tested from January to March 2000 in the Ivory village and the Ambatolahy village: Knox-Out, a microcapsulated formulation of diazinon, organophosphorous compound (240 gr/L) and the deltamethrin powder (2 g/kg ai), respectively. The villages are located 2.5 km apart in the Betafo region in Madagascar. Deltamethrin is a pyrethroid and is still used in the National Plague Control Program, whereas diazinon has not previously been applied in plague control in Madagascar. The flea index and the prevalence of rats carrying fleas in the two villages before and after (at one and two months follow-up, respectively) were measured to evaluate the effect of each insecticide. Flea index decreased significantly in both villages by at the first month follow-up. However, at the second month follow-up no significant differences in comparison to pre-treatment index values were observed in any of the villages. This study has demonstrated a similar immediate effect of deltamethrin and of diazinon, and confirmed the absence of remanent action of the two insecticides.

Animals↗
PubMedDate not supplied

[Differences between two populations of Citellophilus tesquorum altaicus from the Tuva natural focus of plague].

Citellophilus tesquorum altaicus fleas from two natural (Karginsky and Barlyksky) populations have been studied. There are differences between the fleas of these populations in susceptibility to plague microbe. The adaptability and abundance of the causative organism in the body are higher in the fleas of the Barlyksky population. The sizes of the head are significantly higher in the females of the Karginsky population. There are no differences in this index between males. According to all 5 studies signs of chaetotaxia, the chaeta abundance is greater in both females and males of the Karginsky population. The fluctuating asymmetry is higher in the Barlyksky fleas that are more susceptible to the studied type of the causative agent of plague.

Animals↗
PubMed1979

The host/parasite relationships of Xenopsylla astia and X. cheopis on Bandicota bengalensis in Rangoon, Burma.

In Rangoon, Burma, over half the commensal B. bengalensis taken in live traps were found to be infested with Xenopsylla species fleas. X. astia infestations were twice as common as those of the classic plague vector X. cheopis. In terms of absolute numbers X. astia outnumbered X. cheopis by 10 to 1. X. astia was more commonly found as a monospecific infestation, and X. cheopis was more commonly found mixed with X. astia. The flea indicies were high, with a specific index of 2.4 for X. cheopis and 10.2 for X. astia. The flea indicies and flea sex ratios remained stable across the host population and could not be correlated to changes in the head and body length of the host and were not different on male or female hosts. The evidence of this and other surveys is that X. cheopis is not as well adapted for parasitism on free ranging B. bengalensis as is X. astia.

Animals↗
PubMed1982

Plague: review of ecology.

Yersinia pestis, the organism which causes plague in man and animals, circulates from host to host in nature by means of one of many flea vectors. There are about 340 mammals known to be susceptible to plague and over 30 fleas which are known to carry the organism. The habits of flea and host, usually a rodent, must to some extent coincide before infection can be established, and these habits are affected by the temperature and humidity of the environment, by vegetation cover, by season, indeed by everything that is included in the term 'landscape epidemiology'. The ease with which fleas either block or not after feeding is important, but sheer numbers in a focus may sometimes be more important. Some rodents are so highly susceptible that whole colonies may be wiped out by plague, yet alongside these susceptible animals there are usually other resistant hosts which maintain the infection in an area between epizootics.

Animals↗
PubMed1980

Plague in Central Java, Indonesia.

Plague in man occurred from 1968 to 1970 in mountain villages of the Boyolali Regency in Central Java. Infected fleas, infected rats, and seropositive rats were collected in villages with human plague cases. Subsequent isolations of Yersinia pestis and seropositive rodents, detected during investigations of rodent plague undertaken by the Government of Indonesia and the WHO, attested to the persistence of plague in the region from 1972 to 1974.Since 1968, the incidence of both rodent and human plague has been greatest from December to May at elevations over 1000 m. Isolations of Y. pestis were obtained from the fleas Xenopsylla cheopis and Stivalius cognatus and the rats Rattus rattus diardii and R. exulans ephippium. The major risk to man has been fleas infected with Y. pestis of unique electrophoretic phenotype. Infected fleas were collected most often in houses.Introduced in 1920, rodent plague had persisted in the Boyolali Regency for at least 54 years. The recent data support specific requirements for continued plague surveillance.

Animals↗
PubMed1995

Parasites of the Abert's squirrel (Sciurus aberti) and red squirrel (Tamiasciurus hudsonicus) of New Mexico.

Between 1989 and 1991, 29 Abert squirrels (Sciurus aberti) and 45 red squirrels (Tamiasciurus hudsonicus) were collected in New Mexico and examined for parasites. Of 29 S. aberti examined, 86.2% (25/29) were infected with at least 1 parasite species. Helminths were found in 62.1% (18/29) of S. aberti; 37.9% (11/29) were infected with fleas and 37.9% (11/29) with the coccidian Eimeria tamiasciuri. Among T. hudsonicus, 82.5% of the squirrels examined were infected with at least 1 parasite. Helminths were found in 57.8% (26/45) of T. hudsonicus; 22.2% (10/45) were infected with fleas and 26.7% (12/45) with Eimeria tamiasciuri. Citellinema quadrivittati was found in squirrels of both species; 55.2% (16/29) of S. aberti were infected, with 57.8% (26/45) of T. hudsonicus carrying the parasite. Enterobius sciuri was only found in S. aberti with 17.2% (5/29) carrying the infection. One cestode, Hymenolepis sp., was found only in T. hudsonicus with 6.7% (3/45) carrying the infection. Four species of flea were found on squirrels of both species. Ceratophyllus vison was found on 6.9% (2/29) of S. aberti and 6.7% (3/45) of T. hudsonicus examined. Opisodasys robustus was found on 6.9% (2/29) of S. aberti and 8.8% (4/45) of T. hudsonicus examined. Orchopeas caedens caedens was found on 3.4% (1/29) of S. aberti and 6.7% (3/45) of T. hudsonicus examined. Orchopeas neotomae was found on 10.3% (3/29) of S. aberti and 6.7% (3/45) of T. hudsonicus examined. Two species of flea were only found on T. hudsonicus; Orchopeas leucopus was found on 2.2% (1/45) and Oropsylla idahoensis was found on 2.2% (1/45) of the T. hudsonicus examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Plague foci in Viet Nam: zoological and parasitological aspects.

Reported are the results of studies over the period 1989-94 on host-flea complexes in small mammals and their flea ectoparasites in and around a number of human settlements in Viet Nam in which human cases of plague had been found. Collections were also made in savanna and tropical forest areas within a 10-km radius of the settlements. The greatest numbers of small mammals, for the most part Rattus spp., and of the flea ectoparasite Xenopsylla cheopis were found in inhabited areas. X. cheopis was not found on any feral or sylvan mammal further than 0.6 km from settlements. A possible link between wild and commensal mammals may be provided by the flea Lentistivalius klossi, a specific parasite of squirrels and tree-shrews but also found in very small numbers on commensal rats. No zoonotic foci of plague were found in the immediate vicinity of the villages studied and it is most likely that plague persists in a commensal rat-X. cheopis cycle in and around human settlements in Viet Nam.

Animals↗
PubMedDate not supplied

[Effect of certain factors on block formation in Ceratophillus tesquorum and Neopsylla setosa setosa].

Studies were conducted of the effect of temperature and humidity, variant of plague microbe, frequency and duration of feeding and specificity of the host on the blockformation in the souslik fleas C. tesquorum and N. setosa infected with plague. 28 tests on the effect of temperature and humidity on the blockformation were undertaken, for which 14411 fleas of the above species were used. A temperature of 16 to 22 degrees proved to be optimal; at this temperature the number of blocked fleas (C. tesquorum) varied from 21.2 to 42.7% and that of N. setosa--from 41.9 to 54.2%. Marmot variant of plague microbe caused the formation of the "block" in 53.3 to 55.1% of fleas of N. setosa in 3-4 days and in 28.0 to 42.7% of C. tesquorum in 10-14 days after the infection. In C. tesquorum the process of blockformation is affected by the frequency of feeding, in N. setosa--by the duration of each feeding.

Animals↗
PubMed1953

Application of DDT, BHC, and cyanogas in the control of plague in India.

A comparison is made of the results obtained in various parts of India since 1945 with DDT, BHC, and Cyanogas in the control of plague.Antiplague campaigns involving the use of Cyanogas (calcium cyanide) have shown this pulicide to be effective in many cases in keeping down the flea index and in restricting the spread of the disease, although Cyanogas fumigation alone will not stop the annual recrudescence of epidemics. Comparative trials in Madras State showed that insufflation of rat-holes and harbourages with 10% DDT dusting-powder was effective in keeping the flea index below 1 in several villages, while repeated Cyanogas fumigation in the town of Coonoor did not greatly reduce the index there. In another series of experiments, the toxic action of both DDT and BHC (Gammexane) was still evident 84-90 days after dusting, but the DDT was the more powerful pulicide. Cyanogas dusting had no effect in reducing the flea index in these experiments.In their conclusions, the authors consider that DDT, despite a number of instances of its failure, is the most valuable pulicide, followed by BHC and Cyanogas, in that order. A successful antiplague operation, however, depends on the methods used, the dosage of pulicide, and the time and intensity of its application. In addition, to eradicate plague in endemic areas, it is, of course, necessary to continue control efforts during the interepidemic periods.

Animals↗