Murine typhus in children, South Texas

History, Rats, Fleas, and Opossums. II. The Decline and Resurgence of Flea-Borne Typhus in the United States, 1945-2019

Flea-borne typhus, due to Rickettsia typhi and R. felis, is an infection causing fever, headache, rash, and diverse organ manifestations that can result in critical illness or death. This is the second part of a two-part series describing the rise, decline, and resurgence of flea-borne typhus (FBT) in the United States over the last century. These studies illustrate the influence of historical events, social conditions, technology, and public health interventions on the prevalence of a vector-borne disease. Flea-borne typhus was an emerging disease, primarily in the Southern USA and California, from 1910 to 1945. The primary reservoirs in this period were the rats Rattus norvegicus and Ra. rattus and the main vector was the Oriental rat flea (Xenopsylla cheopis). The period 1930 to 1945 saw a dramatic rise in the number of reported cases. This was due to conditions favorable to the proliferation of rodents and their fleas during the Depression and World War II years, including: dilapidated, overcrowded housing; poor environmental sanitation; and the difficulty of importing insecticides and rodenticides during wartime. About 42,000 cases were reported between 1931-1946, and the actual number of cases may have been three-fold higher. The number of annual cases of FBT peaked in 1944 at 5401 cases. American involvement in World War II, in the short term, further perpetuated the epidemic of FBT by the increased production of food crops in the American South and by promoting crowded and unsanitary conditions in the Southern cities. However, ultimately, World War II proved to be a powerful catalyst in the control of FBT by improving standards of living and providing the tools for typhus control, such as synthetic insecticides and novel rodenticides. A vigorous program for the control of FBT was conducted by the US Public Health Service from 1945 to 1952, using insecticides, rodenticides, and environmental sanitation and remediation. Government programs and relative economic prosperity in the South also resulted in slum clearance and improved housing, which reduced rodent harborage. By 1956, the number of cases of FBT in the United States had dropped dramatically to only 98. Federally funded projects for rat control continued until the mid-1980s. Effective antibiotics for FBT, such as the tetracyclines, came into clinical practice in the late 1940s. The first diagnostic test for FBT, the Weil-Felix test, was found to have inadequate sensitivity and specificity and was replaced by complement fixation in the 1940s and the indirect fluorescent antibody test in the 1980s. A second organism causing FBT, R. felis, was discovered in 1990. Flea-borne typhus persists in the United States, primarily in South and Central Texas, the Los Angeles area, and Hawaii. In the former two areas, the opossum (Didelphis virginiana) and cats have replaced rats as the primary reservoirs, with the cat flea (Ctenocephalides felis) now as the most important vector. In Hawaii, 73% of cases occur in Maui County because it has lower rainfall than other areas. Despite great successes against FBT in the post-World War II era, it has proved difficult to eliminate because it is now associated with our companion animals, stray pets, opossums, and the cat flea, an abundant and non-selective vector. In the new millennium, cases of FBT are increasing in Texas and California. In 2018-2019, Los Angeles County experienced a resurgence of FBT, with rats as the reservoir.

Selection of Diagnostic Cutoffs for Murine Typhus IgM and IgG Immunofluorescence Assay: A Systematic Review

Murine typhus is a neglected but widespread infectious disease that results in acute fever. The immunofluorescence assay (IFA) is the "gold standard" to identify IgM or IgG antibodies, although there is a lack of standardization in methodologies. The objective of this review is to summarize 1) the differences in published methodologies, 2) the diagnostic cutoff titers, and 3) the justification of diagnostic cutoffs. Searches were performed by combining the following search terms: "murine typhus," "rickettsia typhi," "immunofluorescence," "IFA," and "serologic" with restrictions (i.e., "rickettsia typhi" or "murine typhus," and "IFA" or "immunofluorescence," or "serologic*"). The search identified 78 studies that used IFA or immunoperoxidase assay (IIP) antibody cutoffs to diagnose murine typhus, 39 of which were case series. Overall, 45 studies (57.7%) provided little to no rationale as to how the cutoff was derived. Variation was seen locally in the cutoff titers used, but a 4-fold or greater increase was often applied. The cutoffs varied depending on the antibody target. No consensus was observed in establishing a cutoff, or for a single-value diagnostic cutoff. In conclusion, there is a lack of consensus in the establishment of a single-value cutoff. Further studies will need to be executed at each distinct geographic location to identify region-specific cutoffs, while also considering background antibody levels to distinguish between healthy and infected patients.

Murine Typhus in South Texas Children: An 18-year Review

BACKGROUND

Murine typhus is a zoonotic infection caused by Rickettsia typhi that remains endemic in South Texas. In 2003, only 9 Texas counties reported murine typhus compared with 41 counties in 2013.

METHODS

A retrospective study of children discharged with a confirmed diagnosis of murine typhus from Driscoll Children's Hospital between January 1998 and September 2016.

RESULTS

Two hundred thirteen children (113 female) 3 months through 19 years of age (mean, 11.2 ± 4.5 years) were identified. Cases occurred throughout the year. Children were admitted after a mean of 7.7 ± 5.3 days of fever. The most common symptoms were fever (100%), poor appetite (71.9%), malaise/fatigue (69.0%) and headache (67.6%). The most common laboratory abnormalities were elevated C-reactive protein, hypoalbuminemia, elevated erythrocyte sedimentation rate, elevated transaminases and elevated band count with normal total white blood cell count. Children defervesced in a mean of 31.87 ± 21.36 hours after initiation of doxycycline. Hospitalization lasted for a mean of 2.7 ± 1.8 days when children were administered doxycycline within 24 hours of admission compared with, 4.1 ± 1.8 days, P ≤ 0.0001 when started later. Eleven patients (5.1%) were admitted to the pediatric intensive care unit and were older, P = 0.0009. No children died.

CONCLUSIONS

Murine typhus is endemic in South Texas. Children who were treated earlier with doxycycline had a shorter hospitalization than were those who began therapy later. Recognition of murine typhus is important to prevent delay in treatment and development of complications.

Acute Febrile Illness and Complications Due to Murine Typhus, Texas, USA1,2

Murine typhus occurs relatively commonly in southern Texas, as well as in California. We reviewed records of 90 adults and children in whom murine typhus was diagnosed during a 3-year period in 2 hospitals in southern Texas, USA. Most patients lacked notable comorbidities; all were immunocompetent. Initial signs and symptoms included fever (99%), malaise (82%), headache (77%), fatigue (70%), myalgias (68%), and rash (39%). Complications, often severe, in 28% of patients included bronchiolitis, pneumonia, meningitis, septic shock, cholecystitis, pancreatitis, myositis, and rhabdomyolysis; the last 3 are previously unreported in murine typhus. Low serum albumin and elevated procalcitonin, consistent with bacterial sepsis, were observed in >70% of cases. Rash was more common in children; thrombocytopenia, hyponatremia, elevated hepatic transaminases, and complications were more frequent in adults. Murine typhus should be considered as a diagnostic possibility in cases of acute febrile illness in southern and even in more northern US states.

A Severe Case of Murine Typhus Presenting With Anemia and Severe Thrombocytopenia

We discuss a child with severe thrombocytopenia and mild anemia admitted to the Hematology service who quickly deteriorated to a life-threatening state. However, once rickettsial disease was considered in the differential diagnosis and empiric doxycycline begun, she quickly and fully recovered. A diagnostic panel, including Rickettsia typhi serology, confirmed the diagnosis of murine typhus but this occurred weeks after she had recovered. Given the potential severity of rickettsial diseases and the ease of modern travel across geographic borders, hematology-oncology providers everywhere must consider rickettsial diseases in their differential diagnosis of critically ill children and begin empiric therapy with doxycycline promptly.

Myositis in a child with murine typhus

A 12-year-old boy presented with fever, lower extremity pain and weakness. Examination revealed paraparesis, thigh and calf tenderness. Labs showed high creatinine phosphokinase and Rickettsia typhi titers. This case illustrates endemic typhus should be considered in the differential diagnosis of myositis especially in areas with high prevalence of the disease. To our knowledge, this is the first reported case of myositis and paraparesis associated with a case of murine typhus.

Murine typhus in Tunisia: a neglected cause of fever as a single symptom

OBJECTIVES

We had for aim to describe the epidemiologic and clinic characteristics of murine typhus in a series of 43 serologically confirmed cases, in our region.

PATIENTS AND METHODS

Serologic screening for IgG and IgM against Rickettsia typhi was performed in 1024 patients during three years (2006-2008). The characteristics of patients with a positive serology were examined retrospectively. One hundred and seventy sera obtained from blood donors were tested to detect IgG against R. typhi to determine the seroprevalence of the infection.

RESULTS

There was evidence of recent R. typhi infection in 43 patients (4.2%) during the study period, and 3.7% of blood donors had IgG against R. typhi. The mean age of patients was 43.1 years and the sex-ratio was 1.04. Among the patients, 58.1% were from rural areas. No patient reported any exposure to rats or rat-fleas. There were more cases during the summer and fall. The most frequent complaint was fever as a single symptom (67.5%). A cutaneous rash was reported in 44.1% and headache in 60.5% of patients. Among the patients, 44.1% presented with thrombopenia and 47.2% with elevated liver enzymes.

CONCLUSION

Murine typhus seems to be frequent in Tunisia. This infection could be a threat for travellers. Serology should be performed systematically in patients with fever as a single symptom since its clinical presentation is non-specific.

Two pathogens and one disease: detection and identification of flea-borne Rickettsiae in areas endemic for murine typhus in California

Results of an environmental assessment conducted in a newly emergent focus of murine typhus in southern California are described. Opossums, Didelphis virginiana Kerr, infested with cat fleas, Ctenocephalides felis Buché, in the suburban area were abundant. Animal and flea specimens were tested for the DNA of two flea-borne rickettsiae, Rickettsia typhi and Rickettsia felis. R. felis was commonly detected in fleas collected throughout this area while R. typhi was found at a much lower prevalence in the vicinity of just 7 of 14 case-patient homes identified. DNA of R. felis, but not R. typhi, was detected in renal, hepatic, and pulmonary tissues of opossums. In contrast, there were no hematologic polymerase chain reaction findings of R. felis or R. typhi in opossums, rats, and cats within the endemic area studied. Our data suggest a significant probability of human exposure to R. felis in the area studied; however, disease caused by this agent is not recognized by the medical community and may be misdiagnosed as murine typhus using nondiscriminatory serologic methods.

Bloodstream infection among children presenting to a general hospital outpatient clinic in urban Nepal

Background

There are limited data on the etiology and characteristics of bloodstream infections in children presenting in hospital outpatient settings in South Asia. Previous studies in Nepal have highlighted the importance of murine typhus as a cause of febrile illness in adults and enteric fever as a leading bacterial cause of fever among children admitted to hospital.

Methods

We prospectively studied a total of 1084 febrile children aged between 2 months and 14 years presenting to a general hospital outpatient department in Kathmandu Valley, Nepal, over two study periods (summer and winter). Blood from all patients was tested by conventional culture and by real-time PCR for Rickettsia typhi.

Results

Putative etiological agents for fever were identified in 164 (15%) patients. Salmonella enterica serovar Typhi (S. Typhi) was identified in 107 (10%), S. enterica serovar Paratyphi A (S. Paratyphi) in 30 (3%), Streptococcus pneumoniae in 6 (0.6%), S. enterica serovar Typhimurium in 2 (0.2%), Haemophilus influenzae type b in 1 (0.1%), and Escherichia coli in 1 (0.1%) patient. S. Typhi was the most common organism isolated from blood during both summer and winter. Twenty-two (2%) patients were PCR positive for R. typhi. No significant demographic, clinical and laboratory features distinguished culture positive enteric fever and murine typhus.

Conclusions

Salmonella infections are the leading cause of bloodstream infection among pediatric outpatients with fever in Kathmandu Valley. Extension of immunization programs against invasive bacterial disease to include the agents of enteric fever and pneumococcus could improve the health of children in Nepal.

Murine typhus in Cyprus: a 9-year survey

Epidemiological and clinical data of 193 human cases of murine typhus in Cyprus were recorded and analysed during a 9-year period (2000-2008). The incidence rate was estimated at 24.5 cases/100,000 population/year. The incidence rate varied considerably between rural, urban and semi-urban areas, with residents in rural areas accounting for 79.3% of the total cases. Most (72.5%) of the cases occurred in late summer (July and August) and early autumn (September to October) with a peak in September. Well-established persistent endemic foci with clusters of cases were identified and characterised as 'high risk' areas. Presence of or contact with rats and fleas, presence of domestic/peridomestic animals and residence in rural areas, especially locations near the 'green line' (a narrow zone patrolled by UN forces that separates the northern and southern parts of the island), increased the possibility of murine typhus infection. The results of the current study enhance the belief that murine typhus is a serious public health problem in Cyprus.

Urban focus of Rickettsia typhi and Rickettsia felis in Los Angeles, California

Classic murine typhus, caused by Rickettsia typhi, is endemic in the continental United States in areas of Texas and southern California. We conducted an environmental investigation in an urban area of Los Angeles identified as the probable exposure site for a case of murine typhus. Four Rattus norvegicus heavily infested with Xenopsylla cheopis (average 32.5 fleas per animal, range 20-42) were trapped, and fleas, blood, and tissues were collected. DNAs from all specimens were tested for R. typhi and Rickettsia felis using a TaqMan assay targeting the rickettsial citrate synthase gene. Although rickettsiemia was not detected, DNA of R. felis was detected in at least one tissue from each rat. Tissues from 3 rats were also positive for R. typhi DNA. R. typhi and R. felis DNAs were detected in fleas collected from each animal with average minimal infection rates of 10% and 32.3%, respectively. Although R. typhi still circulates in urban Los Angeles in the classic Oriental flea-rat cycle, R. felis is more prevalent, even in this association.

Murine typhus in pregnancy

Murine typhus is widely reported in tropical and subtropical areas, especially coastal and port cities. We describe an interesting case of murine typhus in a 26-year-old woman at 26 weeks of gestation treated with ampicillin with a good response. The serology testing for murine typhus was reported after ampicillin was empirically started, and the patient's symptoms were already resolving. To the best of our knowledge, this is the first case report of murine typhus during pregnancy reported in the United States.

Murine typhus in child, Yucatan, Mexico

A case of murine typhus in Yucatan was diagnosed in a child with nonspecific signs and symptoms. The finding of Rickettsia typhi increases the number of Rickettsia species identified in Yucatan and shows that studies are needed to determine the prevalence and incidence of rickettsioses in Mexico.

Murine typhus: an unrecognized suburban vectorborne disease

Murine typhus, an acute febrile illness caused by Rickettsia typhi, is distributed worldwide. Mainly transmitted by the fleas of rodents, it is associated with cities and ports where urban rats (Rattus rattus and Rattus norvegicus) are abundant. In the United States, cases are concentrated in suburban areas of Texas and California. Contrary to the classic rat-flea-rat cycle, the most important reservoirs of infection in these areas are opossums and cats. The cat flea, Ctenocephalides felis, has been identified as the principal vector. In Texas, murine typhus cases occur in spring and summer, whereas, in California, cases have been documented in summer and fall. Most patients present with fever, and many have rash and headache. Serologic testing with the indirect immunofluorescence assay is the preferred diagnostic method. Doxycycline is the antibiotic of choice and has been shown to shorten the course of illness.