Haemobartonellosis in squirrel monkeys (Saimiri sciureus): antagonism between Haemobartonella sp. and experimental Plasmodium falciparum malaria

A hemotropic parasite of the genus Haemo bartonella (rickettsial parasite of the Family Anaplasmataceae) is responsible for latent asymptomatic infection in colony-born Saimiri monkeys. Indeed, many of these animals develop a patent Haemobartonella infection following splenectomy. Such patent parasitism is characterized by an intense Haemobartonella parasitemia which peaks between days 12 and 14 after removal of the spleen and then decreases to become undetectable between days 25 and 30. During the resolving phase of parasitemia, a moderate anemia associated with monocytosis and erythrophagocytosis is observed. In certain Saimiri monkeys, Haemobartonella parasitemia remains latent following removal of the spleen. This indicates that the spleen plays a role but is not necessary to maintain latent Haemobartonella parasitism. It also suggests the existence of heterogeneity in the host immune reactivity to the parasite. Latent or patent haemobartonellosis might raise a problem when Saimiri monkeys are used as experimental hosts of Plasmodium falciparum asexual blood stages, as already noticed with "rodent malaria." Thus we investigated the relationship between Haemobartonella and P. falci parum in splenectomized monkeys. When animals harboring latent Haemobartonella sp. were infected with P. falciparum, the former remained latent and exerted no influence on the course of the P. falciparum parasitemia. In constrast, when P. falciparum was initiated in animals which were in the process of developing patent haemobarto nellosis, the course of the former was protracted and either the animal resisted longer, or it self-cleared the P. falciparum infection. Conversely, patent haemobartonellosis was delayed when splenectomy was performed at different times after initiation of P. falciparum infection in intact monkeys. Our results do not allow us to draw conclusions as to the mechanism(s) of the antagonism between the two parasites, but they emphasize the need to monitor the presence of Haemobartonella when splenectomized Saimiri monkeys are used as experimentals hosts for P. falciparum parasitism.     

Human babesiosis in ireland: Further observations and the medical significance of this infection

Three splenectomized persons in Yugoslavia, California, and Ireland have been reported to be infected by three different Babesia species; two cases were fatal. In a study of the site where the fatal infection was contracted in Ireland, blood samples from 36 persons who had recently been bitten by ticks were inoculated into two splenectomized calves; no response to Babesia divergens was detected. Field-collected Ixodes ricinus ticks inoculated into another splenectomized calf resulted in fever and recovery of the agent of tick-borne fever (Cytoecetes phagocytophilia). This attempt to determine the presence of latent infection in human beings with intact spleens should be repeated on a larger scale in areas with a demonstrably high incidence of Babesia in ticks and animals. Few places in the world are free of piroplasms; their presence may present a hazard to splenectomized persons or to those whose splenic function is deficient.     

Neutrophil myeloperoxidase deficiency associated with canine hepatozoonosis

Hepatozoonosis is a very important disease in dogs in Nigeria. Hepatozoonosis was reported in Nigeria in 18 dogs. The clinical signs included fever, anorexia, loss of weight, lameness, oculonasal discharge and conjunctivitis. Hematologic findings included leukocytosis due to neutrophilia and eosinophilia. Parasitemia varied from 1 to 9% of the circulating neutrophils in the peripheral blood smears of the dogs examined. Hepatozoon canis gametocytes were identified in circulating neutrophils of dogs. Peripheral blood smears from dogs confirmed to have natural H. canis infection were cytochemically stained for myeloperoxidase. Parasitized neutrophils were myeloperoxidase deficient while non-parasitized neutrophils were myeloperoxidase positive. This is considered important, because deficiency of the enzyme may be responsible for poor response of H. canis to chemotherapeutic agents.     

Mycoplasma haemocanis infection--a kennel disease?

Mycoplasma haemocanis (formerly Haemobartonella canis) is a red blood cell parasite that causes disease mainly in immunosuppressed and splenectomized dogs. Clinical outbreak of the disease resulted in failure of a large experimental project. We aimed to identify whether M. haemocanis has increased prevalence in kennel-raised dogs. In a prospective study, we compared the prevalence of M. haemocanis in whole blood (anti-coagulated by use of EDTA) collected from pet dogs (University of Illinois, Urbana Champaign, Ill.; n = 60) with that in blood from dogs raised in three distinct kennels in western Europe (WE; n = 23), eastern Europe (EE; n = 20), and North America (NA; n = 20). Screening included antibody testing and microscopy of blood smears. The presence of M. haemocanis was identified using a polymerase chain reaction (PCR) assay for specific DNA of the organism. None of the pet dogs (0%) was test positive for M. haemocanis DNA. Mycoplasma haemocanis was found in dogs tested at all of the kennels. Infection rate in the three kennels was 30, 35, and 87%, respectively (all P < 0.001 versus control, chi2-test). Latent infection with M. haemocanis was not a single observation in kennel-raised dogs. Prevalence may be higher than that in a pet dog population. The potential exists for these latent infections to adversely affect or confound research results.     

Ancylostoma ceylanicum: immunization with soluble worm extract and responses to challenge infection of dogs

When dogs were immunized with soluble extract of adult Ancylostoma ceylanicum antigen, they were partially resistant to challenge infection in this model of human hookworm infection. Two immunizing doses, each of 1 mg protein suspended in Freund's complete adjuvant, were administered to one group of animals 1 and 3 weeks prior to infection with 5000 larvae. When compared with control dogs given the same infective dose, fecal egg excretion and intestinal adult worm burden in the immunized animals were reduced by 59 and 74%, respectively. Infection had no significant effect on hemoglobin concentrations, mean red cell volumes, total white cell counts, platelet levels, or spontaneous and phytohemagglutinin-induced lymphocyte transformations in both control and immunized animals. Both groups developed an eosinophilia, and lymphocytes from the immunized dogs responded transiently to stimulation with both larval and adult worm antigens. Specific IgM antibodies were transitory in both groups of dogs following infection. IgG antibodies developed significantly 2 weeks after infection in the immunized group; however, they did not appear until 4 weeks after infection in the control group. Both groups developed IgA antibodies 1 week after infection. They were maintained in the control dogs, in contrast to the levels in immunized animals which subsided rapidly 4 weeks after infection. Therefore, when animals are injected with soluble adult worm antigen prior to infection, specific protective immunity is acquired.     

Plasmodium berghei: The spleen in sporozoite-induced immunity to mouse malaria

A/J mice were splenectomized (Splx) or sham-splenectomized (SSplx) prior to administration of a single injection of irradiated sporozoites. Following challenge 7 days after immunization, it was found that none of the splenectomized mice were protected whereas 50% of the sham-splenectomized and intact animals were resistant to challenge. In another series of experiments similar groups, along with mice splenectomized just prior to challenge, were injected with 1.5 × 10⁵ irradiated sporozoites over a 5 week period. This resulted in protection of (1) 60–100% of the animals splenectomized before immunization, and (2) 90–100% protection of the animals splenectomized prior to challenge, as well as the intact and sham-splenectomized mice. Serum levels of antisporozoite antibodies (CSP and SNA) increased during immunization of the intact animals. Only 15–20% of the animals splenectomized prior to immunization presented positive CSP reactions and little if any sporozoite neutralizing activity (SNA) was detected. Serum from intact animals immunized and found resistant to sporozoite challenge was used for passive transfer studies. Immune serum recipients were challenged with small numbers of sporozoites. Only one out of 18 recipients was protected against sporozoite challenge.     

Studies on the Cambodian I strain of Plasmodium falciparum in Aotus monkeys

The Cambodian I strain of Plasmodium falciparum, originally from Kampuchea was adapted for development in three different types of Aotus monkeys. High-level parasitemias were readily produced in splenectomized Colombian A. trivirgatus griseimembra monkeys. Initially, only minimal parasitemias developed in A. t. trivirgatus monkeys from Colombia. However, in one animal, adaptation occurred and high-level parasitemias were obtained during the second recrudescence of the infection. Passage to other A. t. trivirgatus monkeys indicated that the parasite was well adapted for development in splenectomized animals; low to moderate parasitemias were still produced in intact animals. This line of the parasite produced high level parasitemias when inoculated into splenectomized Aotus monkeys from Peru. Infections in Anopheles freeborni mosquitoes were obtained as late as the 7th passage in A. t. griseimembra monkeys and as late as the 7th recrudescence of the infection in an individual monkey (348 days after inoculation). The sporogonic cycle was completed in An. freeborni mosquitoes, and one transmission to an A. t. griseimembra monkey via the bites of infected mosquitoes was obtained.     

Haemobartonellosis in the Domestic Cat

Post-mortem examination of two cases of natural Haemobartonella felis infection in the cat is reported. In both cases haemobartonellosis was confirmed on blood smears from the diseased animals. The most noticeable macroscopic finding was a pronounced general anemia. The microscopic examination revealed hyperplasia of the bone marrow and a moderate extramedullary hematopoiesis in case 1 and in case 2 a reduction of the M/E index in the bone marrow.     

Saguinus geoffroyi as a host for Plasmodium vivax

A monkey-adapted strain of Plasmodium vivax (Achiote) was transferred by trophozoites through 11 serial passages in Saguinus geoffroyi (Titi marmoset). Patent infections developed in both normal (23 of 24) and splenectomized (8 of 9) marmosets. The infections in the altered animals were of greater severity than in the intact subjects as indicated by patent periods ($\text{x}\text{?}\text{= 87}\text{vs}\text{61}\text{days}$) and maximum parasitemias ($\text{x}\text{?}\text{= 35,018}\text{vs}\text{16,218}\text{per mm}{}^3$).Relapses were recorded in 13 of 14 unaltered and 4 of 4 splenectomized animals that survived the primary attack. As evidence for acquired immunity, the mean maximum parasitemias during relapse in the normal animals were $\text{1}\text{8}$ of the values during the primary attack; patent periods were shorter than those in the initial infection. There was also some indication of an acquired immunity in the splenectomized group of animals. However, one splenectomized marmoset experienced a patent period of 325 days during the first relapse.There was considerable variation of infection parameters among the animals in each group.     

IL-5 drives eosinophils from bone marrow to blood and tissues in a guinea-pig model of visceral larva migrans syndrome

This study was undertaken to evaluate the role of IL-5 in eosinophil migration and in the maintenance of eosinophilia in a guinea-pig model of visceral larva migrans syndrome. The results show that the infection of animals with Toxocara canis induced an early increase in serum IL-5 levels that might be essential for eosinophil differentiation and proliferation and for the development of eosinophilia. When infected guinea-pigs were treated with mAb anti-IL-5 (TRFK-5) given at the same time or 1 or 3 days after infection, there was a high percentage of reduction of eosinophil counts 18 days after infection. However, when the mAb was administered during the peak of eosinophilia, there was high inhibition in blood, no inhibition in bronchoalveolar lavage fluid (BALF) or peritoneum and an increase in eosinophil numbers in bone marrow. Thus, a basic level of IL-5 may be essential to drive eosinophils from bone marrow to blood and tissues, and for the maintenance of eosinophilia in infected animals. We may also conclude that when eosinophils have already migrated to the lungs, TRFK-5 has no power to inhibit eosinophilia, which is also under control of local lung cells producing IL-5. In this way, only one later TRFK-5 treatment may not be sufficient to modify the lung parenchyma microenvironment, since T. canis antigens had already stimulated some cell populations to produce IL-5.     

Comparative infectivity of knobless and knobby clones of Plasmodium falciparum in splenectomized and intact Aotus trivirgatus monkeys

In two experiments, two knobless (K-) and two knob-producing (K+) clone-cultures of Plasmodium falciparum, FCR-3/Gambia strain, were injected into four Aotus trivirgatus monkeys. The parasitemia in the K(-)-infected splenectomized (S-) monkey rose to a peak of 2.1% on the 16th day, while it reached only 0.7% at the same time in the K+ infected S- animal. Passage from these animals (karyotype VI) into two intact (S+), naive monkeys of karyotype III resulted in very light infections somewhat higher with K+ than with K-. This experiment was repeated with two different clones in two other S- monkeys of karyotype III. Again, the parasitemia of the K+ infected monkey was appreciably below that of the K- monkey. Transfer of parasites into S+ animals of karyotype II resulted in very light infection and, as before, the K+ did somewhat better. About 2 months after its initial infection, the K(+)-infected S- animal from the second experiment came down with a recurrent malaria infection. Electron-microscopic observations on blood from this monkey revealed that the previously K+ parasites had become knobless (K-). Transfer of this material into an S+, naive monkey, again, gave a barely detectable infection. After splenectomy a recrudescence occurred. The results strongly indicate that K- clones of P. falciparum are more infectious to S- Aotus monkeys than K+ clones, whereas in S+ monkeys the situation is reversed.     

Assessment of prevalence of hydatidosis in slaughtered Sawakny sheep in Riyadh city,Saudi Arabia

Hydatidosis, or echincoccosis, is a serious medical and veterinary problem in many countries, particularly those with rural communities where there is a greater contact between dogs and domestic animals. Domestic livestock act as intermediate hosts which are the main reservoir for the disease in humans. It is therefore very important to estimate the prevalence of hydatid cysts in slaughtered animals since it can be transmitted to humans through dogs, which act as the final host for the disease. From this point of view, the present study was suggested to determine the prevalence of hydatidosis in Sawakny sheep slaughtered in Riyadh city, Saudi Arabia. During the course of the study 12,569 Sawakny sheep were inspected for hydatidosis infection. An overall prevalence of 1.06% was detected among the examined sheep, with the highest prevalence occurring in winter (1.38%) and lowest prevalence in summer (0.67%). Sheep aged 6–12 months had a higher rate of infection than older animals, and males were the predominant carriers of infection (97.7%) compared to females (2.3%). The liver was the most infected organ (79.1%), followed by the lungs (14.6%), while concurrent infections of both the liver and the lungs occurred in 6% of cases. The fertility and viability rates of hydatid cysts in the liver (70.1% and 85.1% respectively) were higher than that in any other organs. In conclusion, it is evident that fertile cysts in slaughtered sheep could have an important role in the continuation of hydatid cyst transmission to humans through dogs. Considerable effort should be devoted to controlling the transmission of cysts from abattoirs by the secure disposal of infected offal. In addition, plans are required for further epidemiological studies and control programs.     

Memory B cells and pneumococcal antibody after splenectomy

Splenectomized patients are susceptible to bloodstream infections with encapsulated bacteria, potentially due to loss of blood filtering but also defective production of anticarbohydrate Ab. Recent studies propose that a lack of Ab is related to reduced numbers of IgM(+) CD27(+) memory B cells found after splenectomy. To test this, we analyzed CD27(+) memory B cell subsets, IgG, and IgM pneumococcal Ab responses in 26 vaccinated splenectomized subjects in comparison to memory B cell subsets and Ab responses in healthy controls. As shown previously, the splenectomized autoimmune subjects had fewer total, isotype switched, and IgM(+) CD27(+) memory B cells as compared with controls, but there was no difference in memory B cells subsets between controls and splenectomized subjects with spherocytosis. There was no difference between the geometric mean IgG Ab response between normal controls and splenectomized subjects (p = 0.51; p = 0.81). Control subjects produced more IgM Ab than splenectomized autoimmune subjects (p = 0.01) but the same levels as subjects with spherocytosis (p = 0.15.) There was no correlation between memory B cell subsets and IgG or IgM Ab responses for controls or splenectomized subjects. These data suggest that splenectomy alone may not be the sole reason for loss of memory B cells and reduced IgM antipneumococcal Ab. Because subjects with autoimmunity had splenectomy at a significantly older age than participants with spherocytosis, these data suggest that an age-related loss of extra splenic sites necessary for the maintenance or function of memory B cells may lead to impaired immunity in these subjects.     

Changes in transthoracic electrical impedance during endotoxemia in dogs.

Our aim was to investigate the role of hematocrit (H) and respiration in transthoracic electrical impedance during endotoxemia. Transthoracic electrical impedance at end-expiratory apnea (Z0) and at end-inspiration (Zmax), H values, and extravascular lung water level (EVLW), estimated by means of gravimetric analysis and the impedance method, were measured in splenectomized and mechanically ventilated dogs. In endotoxemia, there were increases in Z0, Zmax, H and the respiratory frequency. In the splenectomized dogs, both impedances slightly increased without any significant change in H. In the ventilated dogs, Z0, and Zmax increased similarly, while H increased. In the splenectomized, ventilated dogs, no changes were found in the impedances or H. The EVLW values showed that there was no serious edema in the endotoxemic groups. The results suggest that Z0 increased mainly in association with the increase in H. We conclude that the noninvasive measurements of the changes in impedance can be used for continuous monitoring of the fluid and gas shifts in the thorax.     

Molecular epidemiology of hepatitis E virus infections in Shanghai, China

Background

Avian origin canine influenza virus was reported in Korea. The dog to dog contact transmission of the avian origin canine influenza virus (CIV) H3N2 and CIV H3N8 was shown by experimental contact transmission. This study was focused on viral excretion and fever in order to elucidate the epidemiological associations which might be helpful to control the disease transmissions in CIV outbreak in dogs.

Methods

An influenza seronegative 10-week-old Beagle dog was experimentally inoculated with the canine influenza virus A/canine/01/2007, subtype H3N2. Eight hours after inoculation, the infected dog was cohoused with seven uninfected Beagle dogs. Clinical signs including fever were recorded for 14 days post inoculation.

Results

The infected dog and four of seven contact dogs in the study showed clinical signs (sneezing, nasal discharge and coughing) during the study. Viral shedding occurred in all of the animals tested and began on 1 to 6 DPI in dogs with clinical signs. Elevated body temperatures above 39.5°C (geometric mean temperature of 39.86°C±0.49) were observed in all symptomatic dogs. The mean viral titer during fever was 2.99 log EID₅₀/ml, which was significantly higher than the viral titer detected in the non fever.

Conclusions

The data show that contact dogs with a canine influenza infected dog shed different levels of virus in their nasal excretions and demonstrate that clinical signs, including fever, significantly correlate with the viral shedding.     

The Rhesus monkey as a model for the study of infectious disease

Models for bacterial and viral infections and intoxication were developed in rhesus macaques (Macaca mulatta). Manifestations of acute-phase illnesses, e.g., temperature, white blood cell (WBC) counts, blood cultures, etc., were monitored at regular intervals. Viral infection was established by inoculating subcutaneously 412 plaque-forming units of Trinidad strain, Venezuelan equine encephalomyelitis virus. A diphasic febrile response developed, with the first fever peak on days 1 to 2 and a second peak on days 3 to 5. Viremia occurred within 12 hours and persisted in some animals for as long as five days. WBC responses were typical of viral infection. Gram-positive infections were induced by intravenous (IV) inoculation of 10⁸ Type I Diplococcus pneumoniae. Peak febrile response and bacteremia (10² to 10⁶ pneumococci per milliliter) occurred within 48 hours. Gram-negative infections, obtained by IV inoculation with 10⁹ Salmonella typhimurium, induced maximal febrile responses within 24 to 48 hours. Leukopenia occurred in 75% of animals; all were bacteremic. Mortality was 40% at 72 hours. Manifestations of intoxication following IV administration of purified staphylococcal enterotoxin B (10 μg per kg body weight) consisted of vomiting, diarrhea, leukopenia, and fever within one to three hours and resembled nonlethal staphylococcal food poisoning of man. These studies indicate that the rhesus macaque has reproducible and characteristic responses to a variety of microbial stimuli and therefore is eminently suitable for studying pathophysiologic, metabolic, and immunologic parameters of infectious or toxic disease processes.     

Aotus infulatus monkey is susceptible to Plasmodium falciparum infection and may constitute an alternative experimental model for malaria

Aotus is one of the WHO-recommended primate models for studies in malaria, and several species can be infected with Plasmodium falciparum or P. vivax. Here we describe the successful infection of the species A. infulatus from eastern Amazon with blood stages of P. falciparum. Both intact and splenectomized animals were susceptible to infection; the intact ones were able to keep parasitemias at lower levels for several days, but developed complications such as severe anemia; splenectomized monkeys developed higher parasitemias but no major complications. We conclude that A. infulatus is susceptible to P. falciparum infection and may represent an alternative model for studies in malaria.     

Ehrlichia chaffeensis Infection in the Reservoir Host (White-Tailed Deer) and in an Incidental Host (Dog) Is Impacted by Its Prior Growth in Macrophage and Tick Cell Environments

Ehrlichia chaffeensis, transmitted from Amblyomma americanum ticks, causes human monocytic ehrlichiosis. It also infects white-tailed deer, dogs and several other vertebrates. Deer are its reservoir hosts, while humans and dogs are incidental hosts. E. chaffeensis protein expression is influenced by its growth in macrophages and tick cells. We report here infection progression in deer or dogs infected intravenously with macrophage- or tick cell-grown E. chaffeensis or by tick transmission in deer. Deer and dogs developed mild fever and persistent rickettsemia; the infection was detected more frequently in the blood of infected animals with macrophage inoculum compared to tick cell inoculum or tick transmission. Tick cell inoculum and tick transmission caused a drop in tick infection acquisition rates compared to infection rates in ticks fed on deer receiving macrophage inoculum. Independent of deer or dogs, IgG antibody response was higher in animals receiving macrophage inoculum against macrophage-derived Ehrlichia antigens, while it was significantly lower in the same animals against tick cell-derived Ehrlichia antigens. Deer infected with tick cell inoculum and tick transmission caused a higher antibody response to tick cell cultured bacterial antigens compared to the antibody response for macrophage cultured antigens for the same animals. The data demonstrate that the host cell-specific E. chaffeensis protein expression influences rickettsemia in a host and its acquisition by ticks. The data also reveal that tick cell-derived inoculum is similar to tick transmission with reduced rickettsemia, IgG response and tick acquisition of E. chaffeensis.     

The serum IL-12:IL-6 ratio reliably distinguishes infectious from non-infectious causes of fever during autologous stem cell transplantation

BACKGROUND: Fever during neutropenia and after neutrophil engraftment (post-engraftment fever) occurs commonly during autologous transplantation (ASCT), but infections are infrequently identified. Tests that reliably exclude infection may reduce the cost and toxicity of unnecessary diagnostic testing and empiric treatment. We assessed whether serum levels of inflammatory cytokines could distinguish infectious from non-infectious causes of fever in patients undergoing ASCT. METHODS: Serum levels of IL-1beta, IL-2, IL-6, IL-8, IL-10, IL-12(p70), TNF-alpha and IFN-gamma were measured by sandwich ELISA at multiple pre-determined times and at the onset of the first fever during neutropenia and after neutrophil engraftment in patients with hematologic malignancies undergoing ASCT. Standard clinical criteria were used to assess for the presence of infection. RESULTS: Seventy-two febrile episodes occurred in 54 of 65 enrolled patients; 29 (40%) of the episodes occurred after neutrophil engraftment. Infections were identified as the cause of 28% and 24% of the neutropenic and post-engraftment febrile episodes, respectively. The level of IL-12 decreased and that of IL-6 increased significantly during fever because of infection, such that the IL-12:IL-6 ratio accurately excluded infection. The area under the ROC curve for the IL-12:IL-6 ratio was 0.88 (95% CI 0.79-0.97). The sensitivity, specificity, positive predictive and negative predictive values associated with a cut-off ratio of 4.1 were 95%, 75%, 60%, and 97%, respectively. DISCUSSION: The IL-12:IL-6 ratio effectively discriminates infectious from non-infectious causes of fever during ASCT. It may be useful in assessing the probability of infection in patients with post-engraftment fever.