Variable effects of captivity on microbiomes in populations of IUCN-endangered Blanding's turtles (Emydoidea blandingii).

AIMS: Microbiome composition is increasingly considered in species reintroduction efforts and may influence survival and reproductive success. Many turtle species are threatened by anthropogenic pressures and are frequently raised in captivity for reintroduction efforts, yet little is known about turtle microbiome composition in either wild or captive settings. Here, we investigated trends in microbiome composition of captive and wild IUCN-endangered Blanding's turtles (Emydoidea blandingii). METHODS AND RESULTS: We amplified and sequenced the V4 region of the 16S rDNA locus from plastron, cloaca, and water samples of wild E. blandingii adults and two populations of captive E. blandingii juveniles being raised for headstarting. Plastron, cloaca, and water-associated microbiomes differed strongly from each other and were highly variable among captive sites and between captive and wild sites. Across plastron, cloaca, and water-associated microbial communities, microbial diversity changed over time, but not in a predictable direction between captive sites. Plastron beta diversity correlated with growth rate in captive samples, indicating that external microbiomes may correlate with individual fitness. CONCLUSIONS: Our results indicate that external and internal microbiomes vary between captive and wild turtles and may reflect differences in fitness of captive-raised individuals.

Influence of Fuel Properties on the Light Absorption of Fresh and Laboratory-Aged Atmospheric Brown Carbon Produced from Realistic Combustion of Boreal Peat and Spruce Foliage.

Climate change has exacerbated fire activity in the boreal region. Consequently, smoldering boreal peatland fires are an increasingly important source of light-absorbing atmospheric organic carbon ("brown carbon"; BrC). To date, however, BrC from this source remains largely unstudied, which limits our ability to predict its climate impact. Here, we use size-exclusion chromatography coupled with diode array UV-vis detection to examine the molecular-size-dependent light absorption properties of fresh and photoaged aqueous BrC extracts collected during laboratory combustion of boreal peat and live spruce foliage. The atmospheric stability of BrC extracts varies with chromophore molecular size and fuel type: in particular, the high-molecular-weight fractions of both peat- and spruce-BrC are more resistant to photobleaching than their corresponding low-molecular-weight fractions, and total light absorption by peat-BrC persists over longer illumination timescales than that of spruce-BrC. Importantly, the BrC molecular size distribution itself varies with fuel properties (e.g., moisture content) and to an even greater extent with fuel type. Overall, our findings suggest that the accurate estimation of BrC radiative forcing, and the overall climate impact of wildfires, will require atmospheric models to consider the impact of regional diversity in vegetation/fuel types.

A Landmark-Based Technique for Determining an Isometric Femoral Attachment Site for Lateral Extraarticular Tenodesis is Inaccurate.

Purpose: To evaluate the reliability and accuracy of a method of placing the femoral fixation location for lateral extra-articular tenodesis (LET) within a safe isometric area using anatomic landmarks. Methods: Using a pilot cadaveric specimen, the center of the radiographic safe isometric area for femoral fixation of LET, defined as a 1 cm (proximal-distal) area located proximal to the metaphyseal flare and posterior to the posterior cortical extension line (PCEL), was located using fluoroscopy and found to be 20 mm directly proximal to the center of the fibular collateral ligament (FCL) origin. Using 10 additional specimens, the center of the FCL origin and a location 20 mm directly proximal was identified. K-wires were placed at each location. A lateral radiograph was obtained, and distances of the proximal K-wire relative to the PCEL and metaphyseal flare were measured. The location of the proximal K-wire relative to the radiographic safe isometric area was assessed by 2 independent observers. Intrarater and inter-rater reliability was calculated for all measurements using intraclass coefficients (ICCs). Results: There was excellent intrarater and inter-rater reliability for all radiographic measurements (.908 to .975 and .968 to .988, respectively). In 5/10 specimens, the proximal K-wire was outside of the radiographic safe isometric area, with 4/5 anterior to the PCEL. Overall, the mean distance from the PCEL was 1 mm ± 4 mm (anterior), and the mean distance from the metaphyseal flare was 7.4 mm ± 2.9 mm (proximal). Conclusion: A landmark-based technique referencing the FCL origin was inaccurate in the placement of femoral fixation within a radiographic safe isometric area for LET. Therefore intraoperative imaging should be considered to ensure accurate placement. Clinical Relevance: These findings may help to decrease the likelihood of misplacement of femoral fixation during LET by showing that landmark-based methods without intraoperative image guidance may be unreliable.

Intramedullary Metacarpal Fracture Fixation: A Biomechanical Study of Screw Diameter and Comparison With Intramedullary Wire Stabilization.

PURPOSE: Interest in intramedullary metacarpal fracture fixation (IMFF) with screws is increasing. However, the optimal screw diameter for fracture fixation is not yet established. In theory, larger screws should be more stable, but there is concern about long-term sequelae of larger metacarpal head defects and extensor mechanism injury created during insertion as well as implant cost. Therefore, the purpose of this study was to compare different diameter screws for IMFF to a popular and more cost-effective alternative of intramedullary wiring. METHODS: Thirty-two cadaveric metacarpals were used in a transverse metacarpal shaft fracture model. Treatment groups consisted of IMFF with 3.0 × 60 mm, 3.5 x 60 mm, and 4.5 x 60 mm screws as well as 4 1.1-mm intramedullary wires. Cyclic cantilever bending was performed with the metacarpals mounted at 45° to simulate physiologic loading. Cyclical loading at 10, 20, and 30 N was performed to determine fracture displacement, stiffness, and ultimate force. RESULTS: At 10, 20, and 30 N of cyclical loading, all screw diameters tested provided similar stability as measured by fracture displacement and were superior to the wire group. However, ultimate force under load to failure testing was similar between the 3.5- and 4.5-mm screws and superior to 3.0-mm screws and wires. CONCLUSIONS: For IMFF, 3.0, 3.5, and 4.5-mm diameter screws provide adequate stability for early active motion and are superior to wires. When comparing the different screw diameters, 3.5- and 4.5-mm diameter screws offer similar construct stability and strength superior to the 3.0-mm diameter screw. Therefore, to minimize metacarpal head morbidity, smaller screw diameters may be preferable. CLINICAL RELEVANCE: This study suggests that IMFF with screws is biomechanically superior to wires in cantilever bending strength in the transverse fracture model. However, smaller screws may be sufficient to permit early active motion while minimizing metacarpal head morbidity.

Sores of boreal moose reveal a previously unknown genetic lineage of parasitic nematode within the genus Onchocerca.

Long-standing reports of open sores on the hind legs of moose (Alces alces) have been recorded in Alaska (as well as Canada, Europe, and Michigan), eliciting concerns about causes and infection. We used histological and genomic methods to investigate the sores from 20 adult moose on the Kenai Peninsula, Alaska. We paired this with thermal imagery and molt scoring of adult moose to further describe sore formation and understand its timing. Severe, ulcerative and eosinophilic dermatitis was found in all moose with sores present, and microfilariae within intraepidermal pustules were additionally found in four samples. Genetic analysis of sores from moose revealed a previously unknown genetic lineage of Onchocerca. Adult moose molt and lose their barrier of protection against flies in June and July during peak fly activity, leaving them vulnerable and allowing the development of sores. In summary, our results indicate that the cause for the sores on the hindleg of moose is a previously unknown genetic lineage of Onchocerca, probably transmitted by black flies, in timing with the molt cycle of adult moose. These sores leave moose exposed to pathogens, making them vulnerable, and challenging their health and fitness.

Effects of short-interval reburns in the boreal forest on soil bacterial communities compared to long-interval reburns.

Increasing fire frequency in some biomes is leading to fires burning in close succession, triggering rapid vegetation change and altering soil properties. We studied the effects of short-interval (SI) reburns on soil bacterial communities of the boreal forest of northwestern Canada using paired sites (n = 44). Both sites in each pair had burned in a recent fire; one site had burned within the previous 20 years before the recent fire (SI reburn) and the other had not. Paired sites were closely matched in prefire ecosite characteristics, prefire tree species composition, and stand structure. We hypothesized that there would be a significant effect of short vs. long fire-free intervals on community composition and that richness would not be consistently different between paired sites. We found that Blastococcus sp. was consistently enriched in SI reburns, indicating its role as a strongly 'pyrophilous' bacterium. Caballeronia sordidicola was consistently depleted in SI reburns. The depletion of this endophytic diazotroph raises questions about whether this is contributing to-or merely reflects-poor conifer seedling recolonization post-fire at SI reburns. While SI reburns had no significant effect on richness, dissimilarity between short- and long-interval pairs was significantly correlated with difference in soil pH, and there were small significant changes in overall community composition.

Increasing fire and the decline of fire adapted black spruce in the boreal forest.

Intensifying wildfire activity and climate change can drive rapid forest compositional shifts. In boreal North America, black spruce shapes forest flammability and depends on fire for regeneration. This relationship has helped black spruce maintain its dominance through much of the Holocene. However, with climate change and more frequent and severe fires, shifts away from black spruce dominance to broadleaf or pine species are emerging, with implications for ecosystem functions including carbon sequestration, water and energy fluxes, and wildlife habitat. Here, we predict that such reductions in black spruce after fire may already be widespread given current trends in climate and fire. To test this, we synthesize data from 1,538 field sites across boreal North America to evaluate compositional changes in tree species following 58 recent fires (1989 to 2014). While black spruce was resilient following most fires (62%), loss of resilience was common, and spruce regeneration failed completely in 18% of 1,140 black spruce sites. In contrast, postfire regeneration never failed in forests dominated by jack pine, which also possesses an aerial seed bank, or broad-leaved trees. More complete combustion of the soil organic layer, which often occurs in better-drained landscape positions and in dryer duff, promoted compositional changes throughout boreal North America. Forests in western North America, however, were more vulnerable to change due to greater long-term climate moisture deficits. While we find considerable remaining resilience in black spruce forests, predicted increases in climate moisture deficits and fire activity will erode this resilience, pushing the system toward a tipping point that has not been crossed in several thousand years.

Development of the User Requirements for the Canadian WildFireSat Satellite Mission.

In 2019 the Canadian Space Agency initiated development of a dedicated wildfire monitoring satellite (WildFireSat) mission. The intent of this mission is to support operational wildfire management, smoke and air quality forecasting, and wildfire carbon emissions reporting. In order to deliver the mission objectives, it was necessary to identify the technical and operational challenges which have prevented broad exploitation of Earth Observation (EO) in Canadian wildfire management and to address these challenges in the mission design. In this study we emphasize the first objective by documenting the results of wildfire management end-user engagement activities which were used to identify the key Fire Management Functionalities (FMFs) required for an Earth Observation wildfire monitoring system. These FMFs are then used to define the User Requirements for the Canadian Wildland Fire Monitoring System (CWFMS) which are refined here for the WildFireSat mission. The User Requirements are divided into Observational, Measurement, and Precision requirements and form the foundation for the design of the WildFireSat mission (currently in Phase-A, summer 2020).

Prevalence of canine primary hyperparathyroidism recurrence in Keeshond and non-Keeshond dogs after curative parathyroidectomy.

BACKGROUND: Primary hyperparathyroidism (PHPT) is an uncommon condition in dogs, for which there is a documented genetic predisposition in Keeshonden and sporadic cases in other breeds. Secondary literature reports a 10 per cent prevalence for recurrence in patients successfully treated by surgical parathyroidectomy, however there is no published primary literature available on which to base this assertion. This study sought to document prevalence of recurrence within Keeshonden and non-Keeshonden breeds. The authors hypothesised that Keeshonden would have a higher rate of recurrence due to the genetic predisposition for the disease, as compared with sporadic cases in other breeds, and that Keeshonden might have an earlier age of detection of disease. METHODS: A retrospective review of medical records was undertaken to assess the prevalence of recurrence, the length of time after diagnosis that the recurrence occurred, and the age of initial diagnosis in both Keeshonden and non-Keeshonden breeds. RESULTS: The study found that Keeshonden were significantly more likely to develop recurrence (6/12, 50 per cent) than non-Keeshonden dogs (1/15, 7 per cent) (P=0.024), and were significantly younger (median 108 v 126 months, P=0.043) at initial disease detection. Recurrence in Keeshonden occurred at median 35 months after treatment. CONCLUSION: This suggests all dogs treated by curative parathyroidectomy for PHPT should be monitored lifelong for recurrence of disease, and that this is particularly pertinent in the Keeshond population. Earlier screening of younger, apparently healthy Keeshonden may also be advisable.

Short-interval wildfire and drought overwhelm boreal forest resilience.

The size and frequency of large wildfires in western North America have increased in recent years, a trend climate change is likely to exacerbate. Due to fuel limitations, recently burned forests resist burning for upwards of 30 years; however, extreme fire-conducive weather enables reburning at shorter fire-free intervals than expected. This research quantifies the outcomes of short-interval reburns in upland and wetland environments of northwestern Canadian boreal forests and identifies an interactive effect of post-fire drought. Despite adaptations to wildfire amongst boreal plants, post-fire forests at paired short- and long-interval sites were significantly different, with short-interval sites having lower stem densities of trees due to reduced conifer recruitment, a higher proportion of broadleaf trees, less residual organic material, and reduced herbaceous vegetation cover. Drought reinforced changes in proportions of tree species and decreases in tree recruitment, reinforcing non-resilient responses to short-interval reburning. Drier and warmer weather will increase the incidence of short-interval reburning and amplify the ecological changes such events cause, as wildfire activity and post-fire drought increase synergistically. These interacting disturbances will accelerate climate-driven changes in boreal forest structure and composition. Our findings identify processes of ongoing and future change in a climate-sensitive biome.

Is summer food intake a limiting factor for boreal browsers? Diet, temperature, and reproduction as drivers of consumption in female moose.

Food intake may limit the ability of browsing mammals to gain body mass during the growing season when the leaves and stems of woody plants are most abundant. Moose are highly productive browsers with high demands for energy and nutrients, particularly during lactation. Using an indigestible marker, we estimated dry matter intake of free ranging adult female moose with and without calves over three growing seasons. During the same period, we analyzed forage quality. Intakes were highest in late spring (280 ± 19 g·kg-0.75·d-1) when forage quality peaked; however, intakes declined by 39% throughout the summer as temperatures increased and as acid detergent fiber content of browse increased. Digestibility of dry matter declined over summer from 71% to 57% among browse. Intakes were similar for moose with and without calves. Heat loads may impair the ability of moose to consume sufficient energy and nutrients. Warming and habitat change can adversely affect browser populations when poor forage qualities and low dry matter intakes combine to suppress digestible intakes of energy and nutrients.

Blanding's turtles (Emydoidea blandingii) as a reservoir for Leptospira spp.

Leptospira spp. are re-emerging zoonotic pathogens. Previous research has found that Blanding's turtles (Emydoidea blandingii) experimentally infected with Leptospira interrogans shed leptospires in their urine, suggesting that they could play a role in transmitting pathogen within an aquatic ecosystem. This study investigated whether a population of wild Blanding's turtles known to be exposed to Leptospira spp. actively shed the pathogen under natural conditions. Blood samples were collected for serologic testing and to assess the health of the turtles. Free catch urine was collected for polymerase chain reaction (PCR) testing. All turtles were seropositive for Leptospira spp. and 73.5% (25/34) of the urine samples were PCR positive. All animals appeared clinically healthy and showed no apparent signs of disease. This study confirms that wild Blanding's turtles can actively shed Leptospira spp. in their urine and suggests that they may play a role in the epidemiology of this disease in habitats in which they reside.

Successful treatment of Yersinia pseudotuberculosis hepatitis in a cat presenting with neurological abnormalities.

CASE SUMMARY: A 3-year-7-month-old female neutered domestic shorthair cat was presented for further investigation of acute-onset neurological abnormalities, including marked decreased mentation, ataxia and abnormal cranial nerve responses, with concurrent marked pyrexia (40ºC). Initial blood testing was non-specific with mild-to-moderate increases in alanine aminotransferase (ALT) (194 IU/l; reference interval [RI] 17-62 IU/l), aspartate aminotransferase (AST; 150 IU/l [RI 0-51 IU/l]) and total bilirubin (20 µmol/l; RI 0-11 µmol/l), and neutropenia (1.17 ×109/l; RI 2.5-12.5 ×109/l). Brain MRI and cerebrospinal fluid analysis were unremarkable and Toxoplasma serology was negative. Worsening of hepatic biochemical parameters (ALT 265 IU/l, AST 205 IU/l, total bilirubin 42.9 µmol/l) led to further investigations for liver disease, including ultrasound, fine-needle aspirate cytology, histology, fluorescent in situ hybridisation and culture of liver tissue and bile, resulting in a diagnosis of Yersinia pseudotuberculosis hepatitis. The cat was treated with a combination of potentiated amoxicillin (62.5 mg PO q12h), marbofloxacin (5mg PO q24h) and combined s-adenosyl methionine (SAMe)/silybin (90 mg PO q24h), and made a full recovery. Follow-up over 14 months identified a persistent mild increase in ALT, despite no apparent ongoing disease. RELEVANCE AND NOVEL INFORMATION: Yersinia pseudotuberculosis hepatitis should be considered as a differential diagnosis in cats presenting with acute-onset neurological signs, and, when diagnosed, can be successfully treated with a combination of marbofloxacin, potentiated amoxicillin and SAMe/silybin. This is the first such case treated successfully with licensed veterinary antimicrobials and the first instance where Y pseudotuberculosis hepatitis has presented with primarily neurological clinical signs.

EPIDEMIOLOGY OF EMYDOIDEA HERPESVIRUS 1 IN FREE-RANGING BLANDING'S TURTLES (EMYDOIDEA BLANDINGII) FROM ILLINOIS.

Herpesvirus infections have been associated with high morbidity and mortality in populations of captive emydid chelonians worldwide, but novel herpesviruses have also recently been identified in apparently healthy free-ranging emydid populations. Blanding's turtle (Emydoidea blandingii), an endangered species in Illinois, has experienced range-wide declines because of habitat loss, degradation, and fragmentation. A novel herpesvirus, Emydoidea herpesvirus 1 (EBHV1), was identified in Blanding's turtles in DuPage County, IL, in 2015. Combined oral-cloacal swabs were collected from radio transmitter-fitted and trapped (n = 54) turtles multiple times over the 2016 activity season. In addition, swabs were collected at a single time point from trapped and incidentally captured (n = 84) Blanding's turtles in DuPage (n = 33) and Lake (n = 51) counties over the same field season. Each sample was tested for EBHV1 using quantitative polymerase chain reaction (qPCR). EBHV1 was detected in 15 adult females for an overall prevalence of 10.8% (n = 15/138; 95% confidence interval [CI]: 6.2-17.3%). In radio transmitter-fitted females, there was a significantly higher prevalence of EBHV1 DNA in May (23.8%, n = 10/42) than June (3.6%, n = 1/28), July (0%, n = 0/42), August (0%, n = 0/47), or September (7.7%, n = 3/39) (odds ratio: 12.19; 95% CI: 3.60-41.30). The peak in May corresponds to the onset of nesting and may be associated with increased physiologic demands. Furthermore, all positive turtles were qPCR negative in subsequent months. There were no clinical signs associated with EBHV1 detection. This investigation is the critical first step to characterizing the implications of EBHV1 for Blanding's turtle population health and identifying management changes that may improve sustainability.

MEASURING FAT CONTENT USING COMPUTED TOMOGRAPHY TO ESTABLISH A BODY CONDITION INDEX IN FREE-RANGING BLANDING'S TURTLES (EMYDOIDEA BLANDINGII) IN ILLINOIS.

Health assessment of free-ranging populations requires an integrated approach, often incorporating a method to measure mass as a representation of the animals' ability to utilize environmental resources. In chelonians, direct measurements of mass have historically served as a corollary for body condition. However, this method may not accurately represent the true fat volume (FV) and may be skewed by the presence of eggs, shell size, or muscle mass. The objective of this study was to use computed tomography (CT) to develop a model for determining body condition index (BCI) in free-ranging Blanding's turtles (Emydoidea blandingii). Mass, shell measurements, and FV were measured by CT in 65 free-ranging Blanding's turtles from Lake and DuPage counties in Illinois. Twenty-one different models were built for BCI using both FV and fat percentage (FP) as dependent variables. The best fit model for FP included the relationship between mass and carapace length with nearly 60% model support. The model for FV demonstrated a similar relationship but had only 18% support. Linear models with BCI as the dependent variable showed that juveniles had a higher FP than adults and females with more eggs had a lower FP. FP can be calculated in the field with nearly 60% accuracy compared to CT-assessed FP as a component of a physical exam and population health survey to assess the effectiveness of conservation efforts for the endangered Blanding's turtle.

Using Non-destructive Techniques to Measure Mercury (Hg) Concentrations in Gravid Blanding's Turtles (Emydoidea blandingii) in Northeastern Illinois.

Aquatic turtles are suitable biomonitors of wetland ecosystem health because they are long-lived and occupy elevated trophic positions in wetland food webs. This study aimed to determine Hg exposure in adult Blanding's turtles (Emydoidea blandingii), an imperiled prairie-wetland species endemic to the northern U.S. and southern Canada. Claw samples were collected from gravid females from four wetland sites in northeast Illinois. Claw Hg concentrations ranged from 654 to 3132 ng/g and we found no effect of body size (carapace length, CL) and some evidence for an effect of wetland site (WS) on mean Hg (i.e. weak effect of site on Hg, detected between WS1 and WS3). Claw Hg concentrations reported in this study were lower than claw concentrations published for other freshwater turtles (e.g. Chelydra serpentina, Sternotherus oderatus). This is the first Hg-related study on Blanding's turtles and can serve as a reference for other Hg studies in Illinois wetlands.

Wildfire as a major driver of recent permafrost thaw in boreal peatlands.

Permafrost vulnerability to climate change may be underestimated unless effects of wildfire are considered. Here we assess impacts of wildfire on soil thermal regime and rate of thermokarst bog expansion resulting from complete permafrost thaw in western Canadian permafrost peatlands. Effects of wildfire on permafrost peatlands last for 30 years and include a warmer and deeper active layer, and spatial expansion of continuously thawed soil layers (taliks). These impacts on the soil thermal regime are associated with a tripled rate of thermokarst bog expansion along permafrost edges. Our results suggest that wildfire is directly responsible for 2200 ± 1500 km2 (95% CI) of thermokarst bog development in the study region over the last 30 years, representing ~25% of all thermokarst bog expansion during this period. With increasing fire frequency under a warming climate, this study emphasizes the need to consider wildfires when projecting future circumpolar permafrost thaw.

Development and validation of a quantitative PCR assay for detection of Emydoidea herpesvirus 1 in free-ranging Blanding's turtles (Emydoidea blandingii).

Blanding's turtles (Emydoidea blandingii), an endangered species in Illinois, have experienced range-wide declines because of habitat degradation and fragmentation, predation, and road mortality. While ongoing studies are crucial to a thorough understanding of the natural history and demographics in these disjointed Illinois populations, infectious disease threats have been largely unevaluated. Herpesvirus outbreaks have been associated with high morbidity and mortality in populations of captive tortoises and turtles worldwide, including the family Emydidae (pond and box turtles). However, novel herpesviruses including Terrapene herpesvirus 1, Emydid herpesvirus 1 and 2, and Glyptemys herpesvirus 1 and 2, have recently been identified in apparently healthy free-ranging freshwater turtles. In 2015, 20 free-ranging Blanding's turtles in DuPage County, Illinois were screened for a herpesvirus using consensus PCR. A novel herpesvirus species (Emydoidea herpesvirus 1; EBHV1) was identified in two animals and shared a high degree of sequence homology to other freshwater turtle herpesviruses. Two quantitative real-time PCR assays, using EBHV1 primer-1 and primer-2, were developed to target an EBHV1-specific segment of the DNA-dependent DNA polymerase gene and validated. Both assays performed with high efficiency (slope = -3.2; R2 = 1), low intra-assay variability, and low inter-assay variability (coefficient of variation <2% at all dilutions). However, EBHV1 primer-2 displayed less variation and was selected to test clinical samples and five closely related herpesvirus control samples. Results indicate that this assay is specific for EBHV1, has a linear range of detection from 108 to 101 viral copies per reaction, and can categorically detect as few as 1 viral copy per reaction. This qPCR assay provides a valuable diagnostic tool for future characterization of EBHV1 epidemiology.

Missed Opportunities for Preventing Perinatal Transmission of Human Immunodeficiency Virus, Florida, 2007-2014.

OBJECTIVES: Despite declining numbers of perinatally exposed infants, an increase in perinatal human immunodeficiency virus (HIV) infections from 2011 to 2013 prompted this study to identify missed perinatal HIV prevention opportunities. METHODS: Deidentified records of children born from 2007 through 2014, exposed to HIV perinatally, and reported to the Florida Department of Health were obtained. Crude relative risks (RRs) and 95% confidence intervals (CIs) for factors associated with perinatal transmission, nondiagnosis of maternal HIV infection, and nonreceipt of antiretroviral medication were calculated. RESULTS: Of the 4337 known singleton births exposed to maternal HIV infection, 70 (1.6%) were perinatally infected. Among perinatal transmission cases, more than one-third of mothers used illegal drugs or acquired a sexually transmitted infection during pregnancy. Perinatal transmission was most strongly associated with maternal HIV diagnosis during labor and delivery (RR 5.66, 95% CI 2.31-13.91) or after birth (RR 26.50, 95% CI 15.44-45.49) compared with antenatally or prenatally. Among the 29 women whose infection was not known before pregnancy and whose child was perinatally infected, 18 were not diagnosed during pregnancy; 12 had evidence of an acute HIV infection, and 6 had no prenatal care. CONCLUSIONS: Late diagnosis of maternal HIV infection appeared to be primarily the result of acute maternal infections and inadequate prenatal care. In Florida, effective programs to improve utilization of prenatal care and detection and primary prevention of prenatal acute infection are needed.