Seroepidemiology of rickettsial infections in Morocco

Distribution of different Rickettsia species in countries of the WHO Eastern Mediterranean (WHO-EMRO) region: An overview

SUBJECT

Rickettsia is a zoonotic bacterial pathogen transmitted by vectors and has extensive reservoirs in animal and human populations. Rickettsiosis is a public health problem all over the world. However, comprehensive information on the geographical distribution of different Rickettsia species, infection status of reservoirs, vectors, and human cases is lacking in most parts of the world. Therefore, this study aimed to investigate the geographical distribution of different Rickettsia species and their vectors in countries of the WHO-EMRO region.

METHODS

In this review study, a search was conducted for reports and published studies on Rickettsia species from WHO-EMRO region countries in various databases from 1995 to 2022. Finally, the reported status of human cases, reservoirs, and vectors associated with each species in different countries was documented.

RESULTS

Reports of infections related to the detection of Rickettsia species were only available for 15 out of 22 WHO-EMRO member countries. A total of twenty-four Rickettsia species, including R. sibrica, R. lusitaniae, R. africae, R. prowazekii, R. felis, R. typhi, R. rickettsii, R. aeschlimannii, R. conorii, R. massiliae, R. helvetica, R. monacensis, R. rhipicephali, R. bellii, R. asembonensis, R. hoogstraalii, R. andeanae, R. raoultii, R. asiatica, R. slovaca, R. australis, R. barbariae, Candidatus R. amblyommii, and Candidatus R. goldwasserii, were reported from WHO-EMRO member countries. Furthermore, human cases infected with six different Rickettsia species, including R. sibrica, R. prowazekii, R. felis, R. typhi, R. rickettsii, R. aeschlimannii, R. conorii, R. massiliae, and R. helvetica, were reported from these countries.

CONCLUSION

The vast diversity of Rickettsia vectors has contributed to the ongoing discovery of new Rickettsia species. Therefore, further research on the reservoir hosts of Rickettsia infections in the understudied WHO-EMRO region is crucial. This research sheds light on Rickettsia disease's epidemiology and transmission dynamics in this region.

Human-biting ticks and zoonotic tick-borne pathogens in North Africa: diversity, distribution, and trans-Mediterranean public health challenges

North Africa is home to more than 200 million people living across five developing economies (Egypt, Libya, Tunisia, Algeria, and Morocco) and two Spanish exclaves (Ceuta and Melilla), many of whom are impacted by ticks and tick-borne zoonoses. Populations in Europe are also increasingly vulnerable to North African ticks and tick-borne zoonoses due to a combination of climate change and the movement of ticks across the Mediterranean on migratory birds, human travellers, and trafficked wildlife. The human-biting ticks and tick-borne zoonoses in North Africa are reviewed along with their distribution in the region. We also assess present and future challenges associated with ticks and tick-borne zoonoses in North African and highlight opportunities for collaboration and coordination between governments in Europe and North Africa to address public health challenges posed by North African ticks and tick-borne zoonoses.

Coxiella burnetii in Dromedary Camels (Camelus dromedarius): A Possible Threat for Humans and Livestock in North Africa and the Near and Middle East?

The "One Health" concept recognizes that human health is connected to animal health and to the ecosystems. Coxiella burnetii-induced human Q fever is one of the most widespread neglected zoonosis. The main animal reservoirs responsible for C. burnetii transmission to humans are domesticated ruminants, primarily goats, sheep, and cattle. Although studies are still too sparse to draw definitive conclusions, the most recent C. burnetii serosurvey studies conducted in herds and farms in Africa, North Africa, Arabian Peninsula, and Asia highlighted that seroprevalence was strikingly higher in dromedary camels (Camelus dromedarius) than in other ruminants. The C. burnetii seroprevalence in camel herds can reach more than 60% in Egypt, Saudi Arabia, and Sudan, and 70 to 80% in Algeria and Chad, respectively. The highest seroprevalence was in female camels with a previous history of abortion. Moreover, C. burnetii infection was reported in ticks of the Hyalomma dromedarii and Hyalomma impeltatum species collected on camels. Even if dromedary camels represent <3% of the domesticated ruminants in the countries of the Mediterranean basin Southern coast, these animals play a major socioeconomic role for millions of people who live in the arid zones of Africa, Middle East, and Asia. In Chad and Somalia, camels account for about 7 and 21% of domesticated ruminants, respectively. To meet the growing consumers demand of camel meat and milk (>5 million tons/year of both raw and pasteurized milk according to the Food and Agriculture Organization) sustained by a rapid increase of population (growth rate: 2.26-3.76 per year in North Africa), dromedary camel breeding tends to increase from the Maghreb to the Arabic countries. Because of possible long-term persistence of C. burnetii in camel hump adipocytes, this pathogen could represent a threat for herds and breeding farms and ultimately for public health. Because this review highlights a hyperendemia of C. burnetii in dromedary camels, a proper screening of herds and breeding farms for C. burnetii is urgently needed in countries where camel breeding is on the rise. Moreover, the risk of C. burnetii transmission from camel to human should be further evaluated.

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.

Detection of Rickettsia in Rhipicephalus sanguineus ticks and Ctenocephalides felis fleas from southeastern Tunisia by reverse line blot assay

Ticks (n = 663) and fleas (n = 470) collected from domestic animals from southeastern Tunisia were screened for Rickettsia infection using reverse line blot assay. Evidence of spotted fever group Rickettsia was obtained. We detected Rickettsia felis in fleas, Rickettsia massiliae Bar 29 and the Rickettsia conorii Israeli spotted fever strain in ticks, and Rickettsia conorii subsp. conorii and Rickettsia spp. in both arthropods. The sensitivity of the adopted technique allowed the identification of a new association between fleas and R. conorii subsp. conorii species. The presence of these vector-borne Rickettsia infections should be considered when diagnosing this disease in humans in Tunisia.

Serological survey of Q fever in Crete, southern Greece

Coxiella burnetii, the causative agent of Q fever, is an obligatory intracellular bacterium with worldwide distribution. The aim of this study was to determine the prevalence of C. burnetii phase II antibodies in two different groups (high and low risk) of healthy human population and investigate the epidemiological characteristics of the infection in the island of Crete (southern Greece). Collection and testing by IFA of 493 sample sera for IgG and IgM antibodies against C. bumetii phase II antigen indicated a prevalence of IgG antibodies of 48.7%. Of the seropositive individuals, 34% also revealed IgM seropositive antibody titers. Analysis of 225 sample sera by IFA from high risk population presented a prevalence for C. burnetii of 62.2%. Our findings revealed that C. burnetii is highly endemic in Crete, indicating a high exposure of the population to the pathogen regardless of occupation or place of residence.

Seroepidemiologic survey for Coxiella burnetii among hospitalized US troops deployed to Iraq

Q fever is a zoonotic illness which frequently has a non-specific clinical presentation. Cases among deployed US military personnel have been reported in increasing numbers indicating an emerging at-risk occupational group. Banked serum specimens were utilized to estimate seroprevalence and risk factors among military personnel deployed to Iraq. Coxiella burnetii antibody testing was performed and epidemiologic data were analysed from 909 servicemembers. The overall number who seroconverted to Q fever was 88 (10%). The most common ICD-9 code assigned to Q fever cases was fever not otherwise specified (NOS) (45%). A combat occupational specialty was a risk factor for Q fever seroconversion (OR = 1.8, 95% CI: 1.1-2.8) as well as receiving a primary diagnosis of fever NOS (OR = 2.6, 95% CI: 1.6-4.1). These findings indicate that Q fever is a significant infectious disease threat to military personnel deployed to Iraq. A heightened awareness among physicians is necessary to ensure prompt diagnosis and treatment.

Tick-borne rickettsioses, neglected emerging diseases in rural Senegal

BACKGROUND

Rickettsioses are one of the most important causes of systemic febrile illness among travelers from developed countries, but little is known about their incidence in indigenous populations, especially in West Africa.

METHODOLOGY/PRINCIPAL FINDINGS

Overall seroprevalence evaluated by immunofluorescence using six rickettsial antigens (spotted fever and typhus group) in rural populations of two villages of the Sine-Saloum region of Senegal was found to be 21.4% and 51% for spotted fever group rickettsiae for Dielmo and Ndiop villages, respectively. We investigated the role of tick-borne rickettsiae as the cause of acute non-malarial febrile diseases in the same villages. The incidence of rickettsial DNA in 204 blood samples from 134 (62M and 72F) febrile patients negative for malaria was studied. DNA extracted from whole blood was tested by two qPCR systems. Rickettsial DNA was found in nine patients, eight with Rickettsia felis (separately reported). For the first time in West Africa, Rickettsia conorii was diagnosed in one patient. We also tested 2,767 Ixodid ticks collected in two regions of Senegal (Niakhar and Sine-Saloum) from domestic animals (cows, sheep, goats, donkeys and horses) by qPCR and identified five different pathogenic rickettsiae. We found the following: Rickettsia aeschlimannii in Hyalomma marginatum rufipes (51.3% and 44.8% in Niakhar and Sine-Saloum region, respectively), in Hyalomma truncatum (6% and 6.8%) and in Rhipicephalus evertsi evertsi (0.5%, only in Niakhar); R. c. conorii in Rh. e. evertsi (0.4%, only in Sine-Saloum); Rickettsia massiliae in Rhipicephalus guilhoni (22.4%, only in Niakhar); Rickettsia sibirica mongolitimonae in Hyalomma truncatum (13.5%, only in Sine-Saloum); and Rickettsia africae in Rhipicephalus evertsi evertsi (0.7% and 0.4% in Niakhar and Sine-Saloum region, respectively) as well as in Rhipicephalus annulatus (20%, only in Sine-Saloum). We isolated two rickettsial strains from H. truncatum: R. s. mongolitimonae and R. aeschlimannii.

CONCLUSIONS/SIGNIFICANCE

We believe that together with our previous data on the high prevalence of R. africae in Amblyomma ticks and R. felis infection in patients, the presented results on the distribution of pathogenic rickettsiae in ticks and the first R. conorii case in West Africa show that the rural population of Senegal is at risk for other tick-borne rickettsioses, which are significant causes of febrile disease in this area.

Murine typhus as a cause of Fever in travelers from Tunisia and mediterranean areas

BACKGROUND

Travelers are exposed to a variety of health risks in unfamiliar environments and fever is a common problem in patients returning from travel abroad. Rickettsial diseases are increasingly frequently being reported among international travelers. Here we present cases of Rickettsia typhi infection, the agent of murine typhus, that were identified in our laboratory the last year, in travelers from Tunisia.

METHODS

For each patient we tested an acute-phase serum sample and for one patient we tested a convalescent-phase serum sample. IgG and IgM antibody titers were estimated with use of the microimmunofluorescence (MIF) assay. Western blot (WB) assay was performed for all the patients.

RESULTS

We identified three cases of murine typhus after a travel in Tunisia. All cases were observed during late summer and early autumn and patients were suffering by persistent fever. None of them presented rash or inoculation eschar. MIF was positive for Rickettsia sp. in the acute-phase serum samples of two patients. In one patient, two acute-phase serum samples were Rickettsia sp. negative whereas a third convalescent-phase serum sample that was obtained 2 weeks after was Rickettsia sp. positive. By WB assay we identified infection by R typhi. A treatment was immediately started and patients became apyretic.

CONCLUSIONS

In the countries of North Europe, although autochthones cases of murine typhus have not been described, sporadic cases of R typhi infection are identified in travelers who visited murine typhus endemic areas. Murine typhus should be considered in the diagnosis of febrile illness without rash in travelers returning from disease endemic areas, like the south Mediterranean area.

Mediterranean-spotted fever: clinical and laboratory characteristics of 34 children in Oran (Algeria)

INTRODUCTION

Mediterranean-spotted fever (MSF) is endemic in the Mediterranean basin. The aim of our study is to describe clinical and laboratory characteristics of MSF in Algeria.

METHODS

Retrospective study of 34 children suffering from MSF hospitalized from 2002 to 2005. Diagnosis and outcome data were abstracted from patient medical reports. The serological confirmation was obtained by immunofluorescent antibody.

RESULTS

All the children were hospitalized during summer time. The median age was 4.5 years. The sex ratio in the children was 0.76. Clinical features were high fever, maculopapulous rash and black eschar. Among analytical findings, leucocyte count was decreased in 50% of children during the first week of illness. The indirect immunofluorescence for Rickettsia conorii was positive in 70% of cases in the second determination. All received antimicrobial therapy. All children cured without complications.

CONCLUSION

MSF is a mild rickettsial disease in Algeria.

Epidemiology of rickettsioses in North Africa

The first description of Mediterranean spotted fever (MSF) was made by Conor and Brush in 1910 in Tunisia, where, at the same time, Nicolle described the role of lice in transmission of epidemic typhus. However, along this century, there have been few and fragmentary reports about ecology and epidemiology of rickettsioses in North Africa. This region was always considered, for these diseases, like other Mediterranean regions. The most human tick-borne rickettsiosis known to occur in North Africa is MSF caused by R. conorii and transmitted by the brown dog tick, Rhipicephalus sanguineus. Recent studies showed that other arthropode-transmitted rickettsiae are prevalent in North Africa: R. aeschlimannii, R. massiliae, and R. felis. Moreover, R. felis and R. aeschlimannii human infection were respectively confirmed, by serology in Tunisia, and by PCR in Morocco. The seroprevalence of R. conorii among healthy population was ranging from 5% to 8% in most of the countries. Epidemiological and clinical features are frequently resumed in an eruptive fever with eschar occurring in hot season in rural areas. Typhus group rickettsioses, caused by R. typhi and R. prowazekii are less frequently reported than in the 1970s. Seroprevalence of R. typhi among blood donors was from 0.5% to 4%. In Algeria about 2% of febrile patients had R. prowazekii antibodies. Moreover, reemerging threat of epidemic typhus should be considered, after the two cases recently diagnosed in the highlands of Algeria. Murine typhus, considered as "benign" typhus, is underestimated. When R. typhi was inserted in serologic tests, murine typhus became more frequently confirmed. In a recent study in Central Tunisia, we confirmed an emergence of murine typhus mistaken for R. conorii or viral infection. In addition to typhus surveillance, future studies have to determine which spotted fever group rickettsiae are prevalent in vectors and in human pathology.

Epidemiological study of Q fever in humans, ruminant animals, and ticks in Cyprus using a geographical information system

A cross-sectional study of Q fever was conducted in a representative sample of the human and animal population in Cyprus in order to assess the seroprevalence of Q fever and the prevalence of related risk factors. A total of 583 human and 974 ruminant animal serum samples were collected and tested for the detection of antibodies against Coxiella burnetii phase II antigen using an indirect immunofluorescent assay. One hundred forty-one ticks were collected from the infested animals examined; the polymerase chain reaction and the shell-vial technique were used to detect and isolate C. burnetii. Standardized questionnaires were used to obtain information concerning inhabitants and their animals. A geographical information system was used to identify high-risk regions. The prevalence of IgG antibodies against C. burnetii phase II antigen was estimated at 52.7% for humans, 48.2% for goats, 18.9% for sheep, and 24% for bovines. C. burnetii was detected in 11 (7.8%) ticks. Using the geographical information system, two villages were identified as high-risk regions on the basis of high seroprevalence rates of IgG antibodies in humans and animals. Risk factors related to Q fever seropositivity were identified by logistic regression analysis and included age, residence, occupation, use of manure in the garden, ownership of animals (especially goats), and the presence of tick-infested or aborting animals. Q fever poses an occupational hazard to humans living in close contact with sheep and/or goats. In parallel, ticks should be considered an important aspect in the epidemiology of Q fever and should be further studied to better elucidate their role.

Reemergence of Rickettsiosis in Oran, Algeria

The presumptive cases of Mediterranean spotted fever have been identified in 1993 and since that time, its frequency has steadily increased. The prospective study, in summer 2004, was conducted in order to present the descriptive clinic and epidemiology, to identify more severe forms, the presence of the multiple eschars, and different rickettsial strains caused the disease in our region. In Oran, the cases were diagnosed clinically. In Marseille, serum specimens were tested by IFA using the panel of eight rickettsial antigen; Western blot and cross-adsorption studies were also performed in order to confirm the diagnosis. Ninety-three patients clinically diagnosed were recorded from July 3 to October 28, 2004. Eighty percent were male, the mean age was 44.3 years, 90% were exposed to dog and 32% reported tick bites. Clinical signs were as follow: presence of underlying disease (44%), sudden onset (78%), fever (100%), loss of weight (63%), conjunctivitis (43%), and a tache noire was noticed in 70%. Interestingly, two patients had two and three eschars, respectively. The rash was maculopapular (palm and sole) and purpuric in nine cases. Doxycycline was the most antibiotic (91%) with favourable outcome in 91% of the cases. Malignant form with death is reported for three patients (3.2%). Among the 93 patients, 104 serum from 65 patients were tested (serums of others patients were lost or ticket not found on tube. Sixty-three patients out of 65 had a positive serology by IFA with cross-reactive antibodies especially between R. conorii, R. felis and/or R. typhi. Two others negative serology were: one precocious serum and second from the patient, which presented symptoms of MSF and tested two serums, Western blot and cross-adsorption.

Seroepidemiological study of Rickettsia felis, Rickettsia typhi, and Rickettsia conorii infection among the population of southern Spain

Rickettsia typhi and Rickettsia conorii, the etiologic agents of, respectively, murine typhus and Mediterranean spotted fever, are recognized as frequent causes of fever of intermediate duration in southern Spain; in addition, in recent years Rickettsia felis has been detected in potential vectors in this area. Nevertheless, limited data exist regarding the actual prevalence of past infection due to these three pathogens. In the present study, the prevalence of past infection due to R. felis, R. typhi, and R. conorii was determined in a representative population of southern Spain during 2002. In addition, the possible risk factors associated with exposure to these pathogens were investigated. An epidemiological survey was completed by all subjects included in the study. Serum samples were tested by indirect immunofluorescence assay. The prevalence of past infection due to R. felis, R. typhi, and R. conorii among the 504 total subjects was 6.5, 3.8 and 8.7%, respectively. In multivariate analysis, infection due to R. felis was independently associated with a high-risk occupation (one that required working outdoors in nature, close contact with domestic animals, or potential contact with rodents) (OR=5.8; 95%CI 2.1-15.6), while infection due to R. typhi was associated with older age (factor of 1.04 [95%CI 1.008-1.068]) and frequent insect bites (OR=10.3; 95%CI 2.3-45.5). Two factors were associated with infection due to R. conorii: a high-risk occupation (OR=9.3; 95%CI 3.7-23.2), and participation in outdoor activities (OR=7.2; 95%CI 1.4-38.5). The results confirm the widespread prevalence of past infection due to R. felis, R. typhi, and R. conorii in the population of southern Spain.

Rickettsia felis infection, Tunisia

We report, for the first time, serologic evidence of Rickettsia felis and R. aeschlimannii infections acquired in Tunisia from 1998 to 2003. We found that most patients with antibodies against both R. conorii and R. typhi had serologic evidence of R. felis infection.

Investigation of Rickettsia conorii antibodies in the Antalya area

Mediterranean spotted fever, caused by Rickettsia conorii, is a tick-borne infection. Serum samples for screening R. conorii antibodies of professionally exposed persons in the Antalya region, on the Mediterranean coast of Turkey, were analyzed. R. conorii IgG antibodies were detected in 13 of 98 (13.3%) serum samples. Mediterranean spotted fever antibodies were found to be positive in 9.4% of the men and 15.2% of the women (a total of 13 cases). Only three cases had a history of fever and rash.