Correction: Persistence of Borrelia burgdorferi in Rhesus Macaques following Antibiotic Treatment of Disseminated Infection.

[This corrects the article on p. e29914 in vol. 7.].

Low prevalence of Chagas parasite infection in a nonhuman primate colony in Louisiana.

Chagas disease, an important cause of heart disease in Latin America, is caused by the parasite Trypanosoma cruzi, which typically is transmitted to humans by triatomine insects. Although autochthonous transmission of the Chagas parasite to humans is rare in the United States, triatomines are common, and more than 20 species of mammals are infected with the Chagas parasite in the southern United States. Chagas disease has also been detected in colonies of nonhuman primates (NHP) in Georgia and Texas, and heart abnormalities consistent with Chagas disease have occurred at our NHP center in Louisiana. To determine the level of T. cruzi infection, we serologically tested 2157 of the approximately 4200 NHP at the center; 34 of 2157 primates (1.6%) tested positive. Presence of the T. cruzi parasite was confirmed by hemoculture in 4 NHP and PCR of the cultured parasites. These results strongly suggest local transmission of T. cruzi, because most of the infected NHP were born and raised at this site. All 3 species of NHP tested yielded infected animals, with significantly higher infection prevalence in pig-tailed macaques, suggesting possible exploration of this species as a model organism. The local T. cruzi strain isolated during this study would enhance such investigations. The NHP at this center are bred for use in scientific research, and the effects of the Chagas parasite on infected primates could confuse the interpretation of other studies.

Persistence of Borrelia burgdorferi in rhesus macaques following antibiotic treatment of disseminated infection.

The persistence of symptoms in Lyme disease patients following antibiotic therapy, and their causes, continue to be a matter of intense controversy. The studies presented here explore antibiotic efficacy using nonhuman primates. Rhesus macaques were infected with B. burgdorferi and a portion received aggressive antibiotic therapy 4-6 months later. Multiple methods were utilized for detection of residual organisms, including the feeding of lab-reared ticks on monkeys (xenodiagnosis), culture, immunofluorescence and PCR. Antibody responses to the B. burgdorferi-specific C6 diagnostic peptide were measured longitudinally and declined in all treated animals. B. burgdorferi antigen, DNA and RNA were detected in the tissues of treated animals. Finally, small numbers of intact spirochetes were recovered by xenodiagnosis from treated monkeys. These results demonstrate that B. burgdorferi can withstand antibiotic treatment, administered post-dissemination, in a primate host. Though B. burgdorferi is not known to possess resistance mechanisms and is susceptible to the standard antibiotics (doxycycline, ceftriaxone) in vitro, it appears to become tolerant post-dissemination in the primate host. This finding raises important questions about the pathogenicity of antibiotic-tolerant persisters and whether or not they can contribute to symptoms post-treatment.

Modification of a common BAL technique to enhance sample diagnostic value.

Bronchoalveolar lavage (BAL) by means of bronchoscopy is a diagnostic tool frequently used for clinical and research purposes in nonhuman primates. Although many institutions use this procedure, the technique is not standardized. One technical aspect that can vary is the method by which fluid is recovered. The purpose of this study was to evaluate differences between 2 different BAL aspiration techniques. Bronchoscopy and BAL fluid collection were performed on 20 rhesus macaques (Macaca mulatta). Data collected for comparison included heart rate, oxygen saturation levels, rectal temperature, volume of fluid collected, total cell count, cell viability, differential cell count, and flow cytometry. Results showed no significant differences in the heart rate, oxygen saturation, or body temperature between the 2 groups. Likewise, differential cell counts and cell viability studies of the retrieved fluid did not differ between methods. Compared with the conventional technique, the modified aspiration technique led to an 8.3% increase in overall fluid yield and a higher concentration of cells recovered. These differences are statistically significant and likely will be clinically relevant in the context of diagnosis.

Complications of gastric catheters implanted in rhesus macaques (Macaca mulatta).

As part of a study addressing chronic alcohol consumption and simian immunodeficiency virus, 31 rhesus macaques (Macaca mulatta) were implanted with gastric catheters used to deliver alcohol or isocaloric sucrose (control). Once implanted, the animals wore jackets and were housed in specialized cages modified with swivels and tethers. During the course of the study, 3 animals developed clinical signs indicating possible instability of the implanted gastric catheter. All 3 animals were found to have a string foreign body wrapped around the distal end of the catheter, with 2 of the catheters perforating the intestinal wall. Gastroscopy was used to screen remaining animals to determine catheter position and the presence of a foreign body attached to the end of the catheter. Results of the screening revealed that of the 28 remaining animals, 9 had malpositioned catheters; string foreign bodies were associated with 3 of the 9 malpositioned catheters. We initially hypothesized that the peristaltic motion of the stomach, combined with the attachment of string, which was probably ingested by subjects after manipulating their jackets, led to eventual catheter displacement. We later concluded that the string may have played a secondary role but was not the primary cause of catheter instability, because several malpositioned catheters had no string attached at the time of diagnosis. Subsequent modifications were instituted, including modifying the surgical technique, altering the type of gastric catheter used, and increasing environmental enrichment for animals with known tendency to manipulate their jackets.

Age as a determinant of reproductive success among captive female rhesus macaques (Macaca mulatta).

A retrospective analysis was performed on fertility outcomes among a colony of captive Indian rhesus monkeys. The analysis covered over 30 years and was based on 1443 females with a total of 11,453 pregnancies. Various determinants of fertility were assessed including birth rates, pregnancy loss, infant survival, interbirth intervals, and interval from last birth to death. Binary variables were analyzed with generalized linear models with random intercepts, while linear mixed models were used for analysis of continuous variables. Age of the dam was a significant factor in determining whether a pregnancy resulted in a birth and whether an infant survived the first 30 days with primiparous or older mothers being less likely to produce an infant surviving to that age. In contrast, sex proved to be the only significant factor in determining whether an infant lived to 1 year, with females being more likely to survive. The interval between births proved to be affected primarily by dam age, while the late death of an infant depressed the likelihood of an extended time interval between her last birth and her death. Overall, these results demonstrate that maternal age contributes significantly to a decline in fertility and older females can live relatively long periods following birth of their last infant.

Comparison of efficacy of moxidectin and ivermectin in the treatment of Strongyloides fulleborni infection in rhesus macaques.

BACKGROUND: Strongyloides infection may result in clinical disease or confound experimental protocols that utilize non-human primates. There is presently a Strongyloides fulleborni infection rate of approximately 27% in the Tulane National Primate Research Center's breeding colonies despite the routine therapeutic and prophylactic use of ivermectin. METHODS: A study was conducted to determine if moxidectin treatment offers advantages to the intestinal parasite control program. A total of 150 rhesus macaques (Macaca mulatta) that were removed from the breeding colonies due to illness were selected for the study. The animals were randomly assigned to treatment groups with 75 receiving ivermectin and 75 receiving moxidectin. Egg counts were performed on fecal samples collected pre- and post-treatment. RESULTS: Both treatments resulted in decreases in the number of eggs/g in the post-treatment sample as compared with the pre-treatment sample; however, no significant difference was found between treatment groups. CONCLUSIONS: With the data demonstrating a similar efficacy in both ivermectin and moxidectin treated macaques, the benefit of moxidectin treatment relates to biosafety and topical application.

Infectivity of the highly transformable BBE02- lp56- mutant of Borrelia burgdorferi, the Lyme disease spirochete, via ticks.

Infectious Borrelia burgdorferi strains that have increased transformability with the shuttle vector pBSV2 were recently constructed by inactivating the gene encoding BBE02, a putative restriction-modification gene product expressed by the linear plasmid lp25 (Kawabata et al., Infect. Immun. 72:7147-7154, 2004). The absence of the linear plasmid lp56, which carries another putative restriction-modification gene, further enhanced transformation rates. The infectivity of these mutants was assessed previously in mice that were inoculated with needle and syringe and was found to be equivalent to that of wild-type spirochetes. Here we examined the infectivity of spirochetes to ticks after capillary inoculation of Ixodes scapularis nymphs and the subsequent spirochetal infectivity to mice via ticks by using B. burgdorferi B31 clonal isolates lacking lp56 and/or BBE02. The absence of lp56 (but not BBE02) correlated with a lower number of spirochetes in ticks after feeding on mice; this plasmid thus may play a role, albeit not an essential one, in supporting spirochetal survival in the feeding tick. Importantly, however, the absence of lp56 and BBE02 did not detectably influence infectivity to mice via ticks.

Serial electrophysiologic studies in rhesus monkeys with Krabbe disease.

Krabbe disease is a progressive leukodystrophy that results in demyelination in the central and peripheral nervous systems in humans. It has been described in a number of mammalian species including the rhesus monkey. We performed serial nerve conduction studies beginning within the first 2 months of life in four homozygous, two heterozygous, and two normal rhesus monkeys (Macaca mulatta) to characterize the peripheral neuropathy. Mean conduction velocities of the median, ulnar, and tibial nerves were significantly slower in the affected than unaffected monkeys at all ages (P < 0.0001). The conduction velocity differences became more apparent between the affected and unaffected as the monkeys aged. When compared to the unaffected monkeys, the serial conduction velocities suggested occurrence of dysmyelination followed by demyelination in the affected monkeys. These observations provide further insight into the disease process and suggest an early window of opportunity for treating Krabbe disease.

Birth of rhesus macaque (Macaca mulatta) infants after in vitro fertilization and gestation in female rhesus or pigtailed (Macaca nemestrina) macaques.

A study was conducted to assess the possibility of using pigtailed macaques (Macaca nemestrina) as recipients for rhesus macaque (Macaca mulatta) embryos. A total of 250 oocytes were collected from 11 rhesus monkeys during 12 follicular aspirations. We performed 15 embryo transfers with two embryos each into rhesus recipients, which resulted in eight pregnancies, of which two were lost during the second trimester. Among the remaining six pregnant rhesus macaques, two were carrying twins, resulting in the birth of eight infants. Twelve transfers of rhesus embryos into pigtailed macaques resulted in one pregnancy and the birth of one infant. Fetal growth and development were monitored by monthly ultrasound examinations, during which biparietal measurements were taken and compared with those derived from 22 pregnant control monkeys. In vitro fertilization-derived singletons tended to develop faster than did twins and naturally conceived control singletons during the initial months of pregnancy and weighed more at birth than did twins. There were pronounced morphologic changes in the placenta of the rhesus that developed in the female pigtailed macaque. These included an irregular shape, elevated placenta-to-birth-weight ratio, and an abnormal length and diameter of the umbilical cord. Histologic analyses of the rhesus-pigtailed placenta showed evidence of maternal-placental floor infarction and thrombosis of the spiral artery with resulting infarction of the villi. These results demonstrate that pigtailed macaques can carry rhesus fetuses to term, but further studies are necessary to determine the cause of the decreased pregnancy rates and observed placental abnormalities.

Dehydroepiandrosterone-sulfate as a biomarker of senescence in male non-human primates.

Numerous studies have suggested important and varying roles for dehydroepiandrosterone (DHEA) and dehydroepiandrosterone-sulfate (DHEA-S) in primate physiological functions. Despite these numerous claims, specific actions and significance of DHEA and DHEA-S are still equivocal. A decline of these hormones in adult humans may have functional significance, yet there is no clear relationship between functional impairments of aging and the decline in DHEA or DHEA-S levels. This current study attempts to address the natural history of adrenal hormones by presenting non-human primate evidence of the endocrinology of aging; the age-related patterns of adrenal hormone decline in three species of the subfamily Cercopithecinae, Macaca mulatta, Macaca nemestrina, and Papio cynocephalus are compared. It is concluded that DHEA-S and cortisol represent lineage specific markers of senescence among primates and that parallel age-related patterns of DHEA-S and cortisol likely reflect lineage specific effects, or rather, phylogenetic similarities of endocrine senescence. The use of relative adrenal hormone levels to approximate species' life expectancies is discussed.