TICKS AND TICK-BORNE DISEASES

TICKS AND TICK-BORNE DISEASES


The brown dog tick, Rhipicephalus sanguineus


Mediterranean Spotted Fever (MSF) is a tick-borne diseases caused by Rickettsia conorii. The disease is widely distributed in India, Africa, Europe and the Middle East bordering the Mediterranean, sub-Saharan Africa and around the Black and Caspian Sea. The main vector of MSF in the Mediterranean area is the brown dog tick Rhipicephalus sanguineus (A 78).

An outbreak of MSF was investigated by studying questing and parasitic stages of ticks in two settlements of equal size and population located 20 km apart in the Negev Desert. Although high morbidity from SFGR was found in one of the settlements (Kibbutz Ze'elim), no clinical cases were observed in the second (Kibbutz Re'im). Using flagging and CO2-trapping, approximately 9 times more ticks were collected in Ze'elim than in Re'im. Rhipicephalus sanguineus was the dominant species in Ze'elim, whereas in Re'im R. turanicus was the most abundant species. The seasonality of the different tick species and stages, the infestation rate of the domestic and wild animals inside and outside the settlements, the climatic and soil differences prevailing in these sites and the percentage of host animals seropositive to SFGR were examined and significant differences between the two settlements were found. It was also shown that in Ze'elim, 7.1% of dog owners acquired MSF during the period 1984-1989 compared with only 1.4% of people without dogs (A 38, A 43).

Domestic dogs in Ze'elim were studied for infestation with R. sanguineus over a period of one year. The mean number of ticks per dog per month was 16.4. The majority of ticks were adults. Male ticks were more abundant on the ears, whereas female ticks were more abundant on the ears and abdomen of the dogs. A strong correlation between the tick numbers and the ambient temperatures was found (A 47).

Of 549 R. sanguineus specimens examined in 1989/90 from Ze'elim, 7.3% were positive for SFGR when tested by the immunofluorescence technique. In Re'im, 2.2% of 156 R. turanicus were positive. In 1994, 27.4% of the ticks in Ze'elim and 2.6% in Re'im were positive for SFGR. To our knowledge, this is the first report of the infection of R. turanicus with SFGR (A 58).

The morphology of R. sanguineus and R. turanicus as well as of the hybrids between them was studied in the laboratory. It was found that the indices of the spiracular plates of the female and male ticks are convenient and reliable characteristics for distinguishing between them. The validity of the two species was also confirmed by RAPT-PCR by analyzing a 460 bp from the mitochondrial 16S rDNA cistron. The number of substitutions, as compared with some of the other congeners examined, support their classification as separate species. Examination of ticks from different areas of Israel and from different countries of Europe showed that while R. sanguineus is a distinct species R. turanicus is highly polymorphic.

The life-cycle of two closely related tick species of R. sanguineus and R. turanicus was studied under laboratory conditions. Female R. turanicus produced twice as many eggs as R. sanguineus due to greater amount of blood engorged by females and the smaller weight of R. turanicus eggs. In all developmental stages, the weight increase after engorgement, which provides the interstage growth, was greater in R. turanicus. The higher density and the greater height of the dorsal epicuticular folds, as well as the special indentations inside the folds in nymphal R. turanicus, allow this tick to stretch its body during blood engorgement to a greater extent than R. sanguineus. The rate of blood ingestion, egg maturation and metamorphosis of R. turanicus was greater than those of R. sanguineus (A 59).

Absolute and relative weight characteristics of 25 species of three-host exophilic ticks from 5 genera have been compared. Ixodes and Haemaphysalis species differ from Hyalomma species by having lighter unfed females, heavier eggs and, hence, considerably smaller interstage compensatory growth. In Hyalomma, Dermacentor and Rhipicephalus species, the compensatory growth is mainly realized through a large weight increase during nymphal feeding (A 67).

Sequences of the Anaplasma phagocytophilum 16s rRNA gene were detected in five ticks collected in Hyalomma marginatum, Rhipicephalus turanicus and Boophilus kohlsi from roe deer on the nature reserve in the Mount Carmel, Israel. All five sequences were identical to those of A. phagocytophilum strain Ap-Variant 1. This is the first reported evidence to the existence of A. phagocytophilum, the agent of Human Granulocytic Anaplasmosis in Israel (A 114).

The ectoparasite fauna of reintroduced roe deer (Capreolus capreolus) was surveyed in a Mediterranean forest in Israel. Ectoparasites were collected from 4 female hand-reared deer during 2004 and 2005. Seasonality, predilection sites of infestation and the apparent effect of the parasites are presented. This is the first study of roe deer parasites in the East Mediterranean. The ectoparasite fauna included 3 hippoboscid flies (Lipoptena capreoli, Hippobosca equina and Hippobosca longipennis), 4 tick (Rhipicephalus sanguineus, Rhipicephalus turanicus, Rhipicephalus kohlsi and Hyalomma marginatum) and one unidentified trombiculid mite species (A 115)

To study tick-pathogen relationships and pathogenesis of infection caused in model animals by the bite of an infected tick, we attempted to establish a laboratory colony of R. sanguineus persistently infected with R. conorii. R. sanguineus ticks of North American and Mediterranean origin were exposed to R. conorii isolates of African (R. conorii conorii strain Malish) and Mediterranean (R. conorii israelensis strain ISTT) origin. Feeding of ticks upon infected mice and dogs, intra-hemocoel inoculation, and submersion in suspensions of purified rickettsiae were used to introduce the pathogen into uninfected ticks. Feeding success, molting success and the longevity of molted ticks were measured to assess the effects of R. conorii on the survival of R. sanguineus. R. sanguineus larvae and nymphs from both North American and Mediterranean colonies exposed to R. conorii conorii Malish experienced high mortality during feeding and molting or immediately after. On the other hand, exposure to ISTT strain lesser effect on tick survival and resulted in 35–66% prevalence of infection. R. sanguineus of Mediterranean origin were more susceptible to infection with either strain of R. conorii than those from North America (A 131).

 

Additional publications on this subject: C 26, C 45, D 11

 


Publications

A 38. Mumcuoglu, K.Y., K. Frish, R. Galun, B. Sarov, E. Manor and E. Gross.1990. Ecological and epidemiological studies on Mediterranean Spotted Fever in the Negev Desert of Israel. Virginia J. Sci. 41:159‑160.

A 43. Mumcuoglu, K.Y., K. Frish, B. Sarov, E. Manor, E. Gross, Z. Gat and R. Galun. 1993. Ecological studies on the brown dog tick Rhipicephalus sanguineus in Southern Israel and its relationship to spotted fever group rickettsiae. J. Med. Entomol. 30:114‑121.

A 47. Mumcuoglu, K.Y., I. Burgan, I. Ioffe‑Uspensky & O. Manor. 1993. Rhipicephalus sanguineus: Observations on the parasitic stage on dogs in the Negev Desert of Israel. Appl. Exp. Acarol. 17:793‑798.

A 58. Guberman, D., K.Y. Mumcuoglu, A. Keysari, I. Ioffe-Uspensky, J. Miller & R. Galun. 1996. Prevalence of spotted fever group rickettsiae in ticks from Southern Israel. J. Med. Entomol. 33:979-982.

A 59. Ioffe-Uspensky, I., K.Y. Mumcuoglu, I. Uspensky & R.Galun. 1997. Rhipicephalus sanguineus and Rhipicephalus turanicus (Acari:Ixodidae): Closely related species with different biological characteristics. J. Med. Entomol. 34: 74-81.

A 67. Uspensky, I., I. Ioffe-Uspensky, K.Y. Mumcuoglu & R. Galun. 1999. Body weight characteristics of some ixodid ticks: Reflecting adaptations to conditions of their habitats. In: Ecology and Evolution of the Acari. J. Bruin, L.P.S. van der Geest & M.W. Sabelis (eds.), pp. 657-665, Kluwer, the Netherlands.

A 78. Mumcuoglu, K.Y., A. Keysary & L. Gilead. 2001. Mediterranean spotted fever in Israel: a tick borne disease. Isr. Med. Ass. J. 4: 44-49.

A 95. Ioffe-Uspensky, I., I. Uspensky, K.Y. Mumcuoglu & R. Galun. 2005. Rhipicephalus sanguineus and R. turanicus (Acari: Ixodidae): Numerical indices for distinguishing between adults of closely related species in Israel. Proceedings of the 5th International Conferences on Ticks and Tick-Borne Pathogens, University of Neuchatel, Switzerland, August 29-September 2, 2005, p. 171-175.

A 114. Keysary, A., R. Massung, M. Inbar, A. Wallach, U. Shanas, K.Y. Mumcuoglu & T. Waner. 2007. First direct evidence of the prevalence of Anaplasma phagocytophilum in Israel. EID 13: 1411-1412.

A 115. Wallach, A.D., U. Shanas, K.Y. Mumcuoglu & M. Inbar. 2008. Ectoparasites on reintroduced roe deer Capreolus capreolus in Israel. J. Wildl. Dis. 44: 693-696.

A 131. Levin, M.L., L. Killmaster, G. Zemtsova, D. Grant, K.Y. Mumcuoglu, M.E. Eremeeva & G.A. Dasch. 2009. Incongruent effects of two isolates of Rickettsia conorii on the survival of Rhipicephalus sanguineus ticks. Exp. Appl. Acarol. DOI:10.1007/s10493-009-9268-9 (in press).  

C 26. Rufli, T. and K.Y. Mumcuoglu. 1981.Dermatological entomology. 18./19. Ixodidae/Hard ticks and Argasidae/Soft ticks (in German). Schweiz. Rundschau Med. 70:362‑385.

C 45. Podvinec, M., J. Ulrich, T. Rufli and K.Y. Mumcuoglu. 1984. Facialis palsies of infectious origin. Proc. Intern. Symp. Facial Nerve, Bordeaux, Sept. 3.‑6., pp. 283‑286.

D 11. Kassis, I., I. Ioffe-Uspensky, I. Uspensky & K.Y. Mumcuoglu. 1997. Human toxicosis caused by the tick Ixodes redikorzevi in Israel: A case report. Isr. J. Med. Sci. 33: 760-761.