Infectious Disease Alert Updates
By Carol A. Kemper, MD, FACP
Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center
Sexual Distancing vs. Access to Care During COVID
SOURCE: Jenness SM, Le Guillou A, Chandra C, et al. Projected HIV and bacterial sexually transmitted infection incidence following COVID-19-related sexual distancing and clinical service interruption. J Infect Dis 2021;223:1019-1028.
During the COVID-19 pandemic, chronically short-funded public health clinics were forced to redirect personnel and services to meet the demands of the pandemic, resulting in service interruptions for prevention and treatment of human immunodeficiency virus (HIV) and sexually transmitted diseases (STD). Nonetheless, during COVID, many public health departments and STD clinics have documented reductions in cases of gonorrhea (GC) and syphilis, presumably as the result of social (sexual) distancing and not the result of under-diagnosis, at least during the inital few months of the pandemic. How important has the effect of distancing vs. diminished access been on new HIV and STD diagnoses?
To answer this question, these authors adapted a stochastic transmission model to examine the relative impact of sexual distancing and medical service interruption on the estimated incidence of HIV, GC, and chlamydia for a population of ~103,000 men who have sex with men (MSM) in the Atlanta area. They examined various simulated scenarios in weekly time steps, ranging from three to 18 months during the pandemic. Primary outcomes were the incidence of HIV, gonococcal infections, and chlamydia per 100 person-years at 2.5 years, the standardized cumulative incidence over five years per 10,000 disease-susceptible MSM, and the total five-year impact. Service interruptions were projected in four areas of HIV screening, post-exposure prophylaxis, antiretroviral treatment, and STD treatment.
Interestingly, a 50% reduction in sexual partnerships coupled with a 50% decline in access to services during an 18-month period offset each other in terms of new HIV cases (projected number of new HIV cases was net negative 227 cases), but had an enormous protective effect on STD cases (projected decline, -23,800 cases) over a five-year period. But if distancing lasted only three months, and diminished access of care lasted 18 months, an estimated additional 890 HIV cases and an additional 57,500 STD cases would result over a five-year period.
While COVID-19 may have put a dent in people’s sex lives, at least for a few months in March 2020, evidence suggests that behaviors began to rebound as early as June to July 2020. According to this model, sexual distancing for three months or less coupled with ongoing restrictions or diminished access to HIV/STD services for 18 months (what many areas currently are facing) would be the worst-case scenario, with projected increases in both HIV and STDs, with the impact felt for five years. Interestingly, a three-month hiatus in sexual partnering with no reduction in services had little impact on the estimated number of new HIV cases going forward. But even sexual distancing for three months had a big impact on the projected number of STDs over the next five years, effectively reducing the total disease burden.
We do not usually think of GC or syphilis in terms of R0, but, like COVID, STDs present a greater contagious risk than HIV. Data for transmission of HIV have been well described, ranging from 0.05% to 0.1% for men and 0.08% to 0.19% for women during one act of heterosexual sex. In contrast, data regarding the risk of transmission of syphilis is estimated to be ~0.5% to 1.4% per sexual act among MSM (higher for anal sex and lower for oral sex) for either primary and secondary syphilis, whereas the risk of transmission of GC during just one sex act is ~60% to 90% male to female and 20% female to male. Efforts aimed at reducing cases of syphilis and GC — and flattening those curves — therefore are important to maintain, even during a pandemic. In other words, watch out for a big rebound in STDs in the next few months.
Zoonosis in Federal Service Dogs
SOURCE: Meyers AC, Auckland L, Meyers HF, et al. Epidemiology of vector-borne pathogens among U.S. government working dogs. Vector Borne Zoonotic Dis 2021;21:358-368.
Researchers performed an investigation of zoonotic infection in working government service dogs. Monitoring the health of these animals and their potential exposures is important for two reasons: These are highly trained animals and very valuable — and the loss of an animal from illness has significant financial costs. Surveillance for vector-borne diseases also can serve as an indicator of local risk and risk to handlers. Illness also may hamper an entire division — as occurred in Iraq in 2009 when all of the explosive detection-trained dogs contracted Trypanosoma cruzi, handicapping that unit. Heartworm and tick and flea control often is provided as regular maintenance for these animals, and annual testing for heartworm (Dirofilaria immitis), Borrelia burgdorferi, Ehrlichia spp., and Anaplasma spp. has become common.
Blood samples were obtained from > 1,600 animals, 476 of which were from geographically dispersed areas throughout the United States and were randomly selected for this project. All of the dogs were working animals, with a median age of 5.4 years. The majority were male. Most had been trained in Europe, although all the dogs went through three to six months of specialty training at one of four sites in the United States (in Virginia, Alabama, and Texas). More than half (54%) worked for the Transportation Security Administration and 24.6% worked for Border Patrol. The remainder worked for Ports of Entry, Federal Protective Services, the U.S. Coast Guard, or the Secret Service. When dogs are off duty, they generally are kept by their handlers at home, although some may sleep in a group kennel. Most (68%) slept indoors.
Multiple different assays were used to test for antibodies to vector-borne pathogens, including those for D. immitis, B. burgdorferi, E. canis, E. ewingii, A. phagocytophilum, and A. platys. Stepwise testing for Leishmania donovani and L. infantum was performed in a random selection of 100 dogs working in areas endemic for the sandfly vector, and these were run in parallel with T. cruzi immunofluorescent assay (IFA). Various samples also were submitted for multiple real-time polymerase chain reaction (PCR) tests for Lyme, relapsing fever group Borrelia, Rickettsia spp., and Leishmania spp.
Overall rates of infection, in descending order of prevalence, included: T. cruzi (12.2%), Leishmania spp. (2.0%), Anaplasma spp. (1.5%), Ehrlichia spp. (1.3%), B. burgdorferi (0.84%), and D. immitis (heartworm) (0.84%). None of the dogs tested positive for Rickettsia spp. Four animals (0.84%)were co-infected, including one dog with three different infections (T. cruzi, B. burgdorferi, and Anaplasma spp.). D. immitis (heartworm) was found in dogs working exclusively in the Southeast, whereas dogs with Lyme were found throughout the United States except for the Southeast. Both Ehrlichia and Anaplasma infections were found in dogs working only in the Northeast and the Southeast.
The highest prevalence of T. cruzi infection was found in dogs working in the Southeast (16.6%), although dogs working in the Midwest (11.7%) and West (10.9%) also were found to be occasionally positive for T. cruzi. In fact, 22% of the Border Patrol dogs working in the Southeast were discovered to be positive for T. cruzi. Four animals were positive for Leishmania, which can present a diagnostic dilemma, since serologic cross-reactions between Leishmania spp. and T. cruzi can occur, and the amistigote phase is identical. Following a series of stepwise serologic assays, it was decided that two of these four animals likely were infected with Leishmania spp. (most likely L. infantum from the Netherlands, where the animals were bred), whereas the other two dogs could have been infected with either species. The identification of the two dogs with L. infantum was important, providing feedback to the breeders; dogs may serve as a reservoir for human infection with L. infantum.
Echinococcus in Saskatchewan
SOURCE: Schurer JM, Tysbina P, Gesy KM, et al. Molecular evidence for local acquisition of human alveolar echinococcosis in Saskatchewan, Canada. J Infect Dis 2021;223:1015-1018.
A 70-year-old male was diagnosed with alveolar echinococcosis (AE) in Saskatchewan, Canada, although he had never traveled outside of North America. Where did it come from?
He was a hunter and owned dogs, although none had been sick from hydatid disease. He originally presented with abdominal pain, splenomegaly, and a 6 cm hepatic mass on imaging with retroperitoneal lymphadenopathy. A biopsy showed chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). He was treated — and his symptoms improved, but he presented two years later in 2018 with a hepatic mass twice the size of the original. A biopsy now showed CLL/SLL plus hydatid disease. Enzyme-linked immunoassay (ELISA) was positive for Echinococcus granulosus, or cystic echinococcus. He was treated with mebendazole, followed by radical resection and then albendazole, and his disease resolved on follow-up imaging.
His tissue was sent to the University of Saskatchewan, where polymerase chain reaction (PCR) targeting of the rrnS ribosomal ribonucleic acid (RNA) gene of E. granulosus and the nad2 mitochondrial gene of E. multilocularis was performed. Comparison with sequences from Saskatchewan coyotes and deer mice showed the human isolate was a 100% match to isolates from two Saskatchewan coyotes at the nad2 locus of E. multilocularis and a 99% match to that of a dog with AE found in British Columbia. Haplotype analysis showed these isolates grouped within the E3/E4 strains of E. multilocularis, originally identified in a red fox in France.
Fewer than 10 cases of autochthonous human AE have been described in Canada, although human cases generally have been limited to the Northwest bordering Alaska and the central prairies. Underreporting may be an issue, since cases of AE are being found increasingly in dogs, lemurs, and deer mice outside of these areas, suggesting expansion of the endemic area. Many of these cases appear related to European strains of E. multilocularis. Molecular techniques confirmed the species identification in this unique human case (different from the serology) and the relationship of this case to European strains of E. multilocularis, suggesting E. multilocularis is an emerging zoonosis in this part of Canada.
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